The association between farming occupations and the incidence of non-Hodgkin's lymphoma (NHL) was examined in a case-control study using a cancer registry to identify cases and controls and death certificates to determine the occupation and industry of employment of cancer patients. Case subjects were white males with a diagnosis of NHL who died between 1967 and 1982; control subjects were white males who died of colon cancer during the same period. Control and case subjects were frequency-matched for age and year of diagnosis; county of residence was not a matching variable. Death certificates with codable occupational information were located for 90% of the 249 case and 293 control subjects. A stratified analysis using test-based confidence intervals revealed an increased risk of NHL among farmers. The overall odds ratio, controlling for age and for year of diagnosis, was 1.3 (90% confidence limits 0.9-2.3). For diagnoses during 1952 through 1965, the odds ratio was 6.6, and for diagnoses during 1966 through 1971, the odds ratio was 3.1. The increased odds ratio was most pronounced among those aged 45 to 64 years at the time of diagnosis and those living in rural counties.