Increased risk of multiple myeloma was found among farmers in studies reported in the literature. A retrospective cohort study of Swedish agricultural workers is now presented. All 254417 men aged 20-69 years at the time of the national census in 1960, who stated that they were working in agriculture, formed the study cohort. The reference cohort consisted of 1725845 men otherwise gainfully employed. The cohorts were followed from 1 Jan 1961 until 31 Dec 1979. The cases of multiple myeloma were identified in the Swedish cancer register by computerized record linkage. The 568 cases found in the study cohort resulted in an estimate of the relative risk of 1.20 (95% confidence interval 1.09-1.33).