The Internet has long drawn people seeking information about health care. Last year, health Web sites drew about 72 million unique visitors, up 14% from a year earlier, according to comScore Inc., an online-marketing research firm that tracks some 200 such sites. Such strong growth comes as sites increasingly focus on some of today's leading consumer health concerns, including prescription-drug safety, quality of care, and the ability to network with other patients facing similar health problems.

Health-care information providers have seen big changes over the past year or so. Two of the most popular sites, Revolution Health and EveryDayHealth, merged to surpass longtime leader WebMD Health Corp. as the largest health site as measured by unique visitors. Google Inc. and Microsoft Corp. launched competing ventures that allow patients to store their medical records online. And HealthCentral Network sold a minority investment to Barry Diller's IAC/Interactive Corp. and the two companies set up a partnership to sell advertising to pharmaceutical companies.

While many health Web sites have enriched their offerings, privacy issues remain a concern as users are able to enter personal information and receive customized alerts and health messages. Consumers should read the privacy policies of the sites carefully and be sure to opt out of any features that share personal information with marketers if they don't want to be contacted.

Advertiser-supported sites can be very useful and are chock-a-block with health information. But they can bombard users with ads. Sites offered by the government and nonprofit groups generally carry no ads, though some nonprofits may receive support from companies or foundations.

Here are some free new sites, or ones that have been recently expanded, that are worth checking:

Consumermedsafety.org: This new site is sponsored by the Institute for Safe Medication Practices, a nonprofit watchdog group that tracks and analyzes reports, mainly from hospitals and health-care professionals, of medication errors and safety risks. The site offers consumers various methods for learning about medication safety. It also allows users to report to the institute, anonymously if they prefer, on problems or safety concerns with medications, including adverse reactions. The site, in partnership with iguard.org, a free drug-safety-alerting service, allows users to sign up for personalized news alerts on manufacturers' drug recalls and alerts issued by the Food and Drug Administration. My favorite feature: Fill out an online form on the medications you take, and the institute will send you information on drug-safety ratings, possible interactions among your medications, side effects and reviews from other patients.

WhyNotTheBest.org: This new site from the nonprofit Commonwealth Fund compares care at 4,500 hospitals nationwide, using data from Medicare's Hospital Compare Web site and the federal government's Hospital Consumer Assessment of Healthcare Providers and Systems survey. The site is primarily aimed at health professionals, but consumers also can readily check on their local hospitals. By entering New York City in the site's search engine, for example, I was able to compare how 17 hospitals in my city performed on various measures of safety and good care. Two such measures: How often a hospital gives surgical patients treatment to prevent blood clots, and how often heart-attack patients are given aspirin on arrival (two gauges of appropriate care used by Medicare and others that should be followed but aren't always).

HazMap (hazmap.nlm.nih.gov): This federal database is designed to provide health and safety professionals and consumers with information about exposure to chemicals and biologic substances at work and with certain hobbies. The site recently added 180 new chemical profiles, and now covers more than 2,000 chemical agents and 225 occupational diseases. Consumers can search by symptoms or diseases. For example, a painter or dry-cleaning worker exposed to solvents can search by job type to learn of potential reactions such as dizziness, headache and lung irritation. And by searching through types of diseases, workers can learn of occupational hazards, such as an association between stomach cancer and rubber workers. Also worth checking is the related ToxTown site at www.toxtown.nlm.nih.gov, which has consumer-friendly information on toxic chemicals and environmental-health risks.

EverydayHealth.com: The site, which recently merged with Revolution Health, links 24 separate health sites catering to various interests. The pregnancy-information site, for instance, is based on a best-selling series of books and is found at WhatToExpect.com. Another, CarePages.com, allows hospitalized patients and families to set up their own Web sites to keep relatives and friends posted on the patient's progress. EverydayHealth.com also allows consumers to create personalized home pages with health news and advice tailored to their interests, or to join community groups or start their own health blog. Another useful feature is calculators, including ones for calorie intake and body-mass index.

Overall, the combined sites had more than 25 million unique visitors in November, according to comScore. The popular WebMD site, by comparison, had about 18.2 million visitors that month. WebMD has expanded its offerings to include a new interactive diet and nutrition center and has struck a deal with the FDA to send public-health alerts to registered users.

HealthCentral.com: This is a network of sites covering various conditions such as attention deficit hyperactivity disorder and diabetes. Users can sign up for news alerts and updates, join communities and watch videos of experts discussing treatments. The home page has a cool symptom checker that can be used to check by gender and body part. I clicked on "woman" and "legs" to answer several questions about the onset and severity of pain in my hip (yup, it could be the early onset of arthritis). But the ads can be intrusive -- to advance beyond the first section of a news story on the health risks of clearing snow from your driveway, I had to click past an ad for a new snow blower.

Google Health (google.com/health) and Microsoft Health Vault (healthvault.com): The rival sites offer a number of health-management tools. Google's site, for instance, allows users to refill prescriptions online at participating local drugstores and to seek a second opinion on a medical question via an online consulting service from partner The Cleveland Clinic (for a $565 fee). Microsoft's features include programs that can link to home devices such as a blood-glucose meter or a heart-rate monitor to track readings and provide them to physicians.

But the sites' main benefit is that it allows individuals and families to create their own free online medical records, and to share these with physicians if they choose. Despite concerns about security and privacy, there is something pretty appealing about having your medical history, medication lists and lab reports on a secure Web site that you can get to in an emergency, particularly since most doctors still haven't switched to electronic medical records in their offices. But for backup, I still advise my mother's strategy: keeping paper copies of everything.