• CDC
  Main page for Centers for Disease Control and Prevention, part of the US Department of Health and Human Services.
• clinicaltrials.gov
  National Institute of Health site providing information on over 29,000 federal and privately sponsored clinical trials. Includes consumer information on the nature of clinical trials and answers to common questions about participation in clinical trials.
• Lab Tests Online
  Contains detailed information about laboratory tests organized both by test and by disease.
• MedLine Plus
  Consumer health information provided by the US National Library of Medicine and the National Institutes of Health.
• MerckSource
  A portal for healthcare information, including a health encyclopedia, medical dictionary, interactive body guide, resource library on medical tests and procedures and surgery information, a symptom checker, interactive body guide, 3D medical animations, and recent health news.
• NIH
  Main page for the National Institute of Health. Includes links to all the various individual National Institutes, including the National Cancer Institute, National Heart, Lung, and Blood Institute, National Institute on Drug Abuse, National Institute of Mental Health, and National Institute of Neurological Disorders and Stroke.

Last full review/revision September 2006