A meta-analysis of studies examining the association between non-Hodgkin's lymphoma (NHL) and employment as a farmer in the central United States was performed to verify the observation by Blair et al.  that this group is at excess risk of NHL. Six studies were selected for the meta-analysis, and the estimator of relative risk calculated was 1.34 (95% confidence interval (CI) = 1.17, 1.55). Exposures associated with NHL and associated with agricultural commodities frequently produced in the central United States are infectious microorganisms and pesticides. Examination of the production patterns of the farms in this region did not reveal a single specific risk factor consistently found on all farms; however, past production patterns suggest that exposure to either infectious microorganisms or pesticides might be a risk factor for NHL in this group of farmers.