Abstract: Records, mainly 1930-1975, of the Wisconsin Medical Society (formerly the State Medical Society of Wisconsin, a private, professional organization of Wisconsin physicians founded in 1841 to promote research, education, and legislation on health and medical issues. The collection documents the Society's governance and activities, and changes in Wisconsin physicians' concerns, attitudes, and practices over the years. It contains extensive information on the early development of prepaid sickness insurance plans; the development and administration of Wisconsin Physicians Service insurance plans; distribution of medical care to the poor in Wisconsin, especially before World War II; medical malpractice issues, including the founding of the Wisconsin Health Care Liability Insurance Plan (WHCLIP); and the Society's attempts to monitor chiropractors and homeopathic health practitioners. The records also contain biographical information on many deceased physicians who were members.