A cohort of approximately 120,000 male and 85,000 female farmers registered in the Farm Register of Finland was followed-up for cancer incidence through the Finnish Cancer Registry in 1979-93. Nearly 17,000 cancer cases were observed. Compared with the total cancer incidence of the Finnish population, both genders experienced a 17 to 18 percent decreased risk of cancer. The risks were low in smoking-related cancers, cancers associated with an urbanized way of life, and cancers inversely associated with multiparity. The only cancer sites showing significantly raised standardized incidence ratios (SIR) were lip cancer (SIR = 1.51, 95 percent confidence interval [CI] = 1.35-1.66) and Hodgkin's disease (SIR = 1.35, CI = 1.08-1.67) in males. Poisson regression was used in working out the roles of the size and type of farm after adjustment for gender, age, and geographic location of the farm. Risk of Hodgkin's disease was highest in farms without animals (SIR = 1.74, CI = 1.12-2.59). Multiple myeloma was found in excess among farmers on pig or poultry farms but not on other types of farms.