Census and hospital discharge data from Sweden and Denmark and U.S. Veterans hospitals, linked for follow-up to cancer, mortality, and population registries where available, were used to assess cancer risk among individuals with specific medical and occupational exposures. Mortality among diabetics in Sweden was elevated for all major causes of death, particularly circulatory, respiratory, digestive, genito-urinary, and malignancies. The youngest diabetics had the greatest increased mortality from all causes. Obese Swedish patients were at increased risk of cancers of the digestive tract, urinary tract, female reproductive organs and connective tissue. Swedish patients with hemochromatosis had a cumulative risk of hepatic cancer of 10% after about nine years. Swedish Celiac patients had an increased risk of lymphoma and cancers of the upper digestive tract. Swedish psoriasis patients were at increased risk of several cancers associated with alcohol and tobacco consumption, but they had no increase in malignant melanoma. Swedish and Danish acromegaly patients were at increased risk of several cancers, including cancers of the small and large intestine, rectum, brain, thyroid, kidney and bone. Several possible mechanisms could be involved, such as the elevated levels of IGF-1 in these patients. In Danish and U.S. Veterans hospital data, we investigated the link between inflammatory bowel diseases (ulcerative colitis and Crohn's disease), appendectomy and cancer. We found no evidence of a reduced risk of ulcerative colitis subsequent to appendectomy in either Danish patients or U.S. veterans. Danish women with molar pregnancy were not found to be at increased risk of any cancer other than gestational choriocarcinoma. Danish women hospitalized with gonorrhea were at increased risk of cervical pre-neoplasia, but not invasive cervical cancer or any other cancers. Danish women with anorexia nervosa had a non-significantly reduced risk of subsequent cancer, which is consistent with the theory that energy restriction may decrease tumor development. Swedish men and women employed in occupations exposed to diesel engine emissions showed increased risks of respiratory and digestive cancers, and also cervical cancer among women. Swedish women employed in paper packaging, graphic work, dry cleaning, telegraph and telephone work were at increased risk of ovary cancer. Prostate cancer incidence, but not mortality, was elevated for Swedish men employed in sedentary occupations in 1960 and 1970. A study of Swedish construction workers found that even small excesses in weight or blood pressure were associated with increased risk of renal cell cancer, and reduction in blood pressure was associated with reduced cancer risk. A large new study was initiated this year to assess familial aggregation of autoimmune diseases and lymphoproliferative malignancies (LP). We will study 50,000 Swedish and 10,000 Danish cases of LP, a smiliar number of non-cancer controls, and all their relatives' computerized medical data (cancers and hospital diagnoses).