Headaches: the common malady: looking for more than an aspirin to fight off your headache? Here are some of the best online information sources we've found.

Ninety percent of adults have had a headache in the past year. At the very least, the pain they cause is a frustrating annoyance. For many, it can be a chronic and incapacitating condition.

The most common type of headache is tension--a steady ache that affects the whole head. Generally tension headaches are caused by a buildup of stress. Sinus headaches can be caused by environmental factors, allergies, or sinusitis.

Cluster headaches are so named because they come in clusters (lasting several weeks). They are relatively rare, affecting only 1 percent of the population. The attacks are acute but relatively short (lasting no more than a couple hours).

Migraines are a most debilitating type of headache. Generally one side of the head pulses or throbs, and the headache is often accompanied by nausea or sensitivity to noise or light. Migraines can be triggered by foods, hormonal imbalances, weather changes, or environmental factors.

For more information about headaches, check out these Web sites:

The American Council for Headache Education (ACHE), at www.achenet.org, is a national nonprofit organization of physicians and patients with 35,000 members. ACHE brings you information about headaches and their prevention and treatment. There is a special section on children's headaches and a glossary of headache terms. The excellent Resources segment includes books, a searchable database of articles, a directory of support groups, and links to relevant Web sites. In addition to their Web site, ACHE publishes a quarterly newsletter, brochures, and other educational materials.

The National Headache Foundation (NHF) at www.headaches.org, is an organization of members who are interested in headache information. The site has topic sheets on specific conditions, diet information, and stress-reducing techniques, as well as information on local support groups in all 50 states. In addition, NHF publishes a newsletter, audio-tapes, videotapes, and books.

Headache Care, at www.headachecare.com, is a network of more than 9,000 primary care providers dedicated to the understanding and treatment of headaches through research, education, and self-management. Visitors to the site will find a collection of current articles from popular media, as well as information on types of headaches, treatment, and prevention. To encourage a sense of community, message boards and a chat room are available. There is also a national directory of physicians.

The World Headache Alliance, at www.w-h-a.org, an international group of lay organizations that aim to provide current and comprehensive information for people who suffer from severe headaches. The information section keeps viewers up-to-date on the latest advances in the management of headaches. Included here are recently published articles and research studies. This area also provides links to, and reviews of, related Internet sites. In the Community area, visitors can chat with headache sufferers from around the globe and get tips on communicating with doctors more effectively. The things to do section includes a History of Headaches and a Headache Quiz.

The American Headache Society, at www.ahsnet.org, is a professional society dedicated to the study and treatment of headache. Here you will find headache diagnosis and treatment information geared for health professionals.

Headache Cybertext, at www.upstate. edu/neurology/haas/index.html, is primarily for doctors and discusses the diagnosis and treatment of headaches. The site is the work of David C. Haas, M.D., professor of neurology and headache specialist at the State University of New York Upstate Medical University in Syracuse, New York. He has compiled timely and informative articles, organized by type of headache. Information is updated frequently, keeping the site current with medical literature. Links to other sites are provided as well.

The JAMA Migraine Information Center, at www.ama-assn.org/special/migraine/migraine.htm, an excellent site from the Journal of the American Medical Association, is designed for the general public and has much accurate and timely information. Newsline includes stories and in-depth special reports. In the Library section you can get information from current articles. The Education and Support Center contains resources for patients as well as professionals. The Treatment Center provides clinical guidelines. And the Best of the Net has links to other Web sites.

Migraine Awareness Group: National Understanding for Migraineurs, at www.migraines.org, contains a wealth of information for migraine sufferers. Topics covered range from Migraines: Myth and Reality to information about disability, impairment, treatment, and management of migraines. In Where to Turn for Help are found numerous links to other migraine and general headache sites.

Yvona Fast is a writer living in Lake Clear, New York.