Agriculture is one of the most hazardous occupations in the United States. We examined the work-related injury rate and risk factors among 290 Iowa male principal farm operators using a population-based, prospective study. Baseline data were collected between 1991 and 1994, and injury events were surveyed in the fall of 1995. Cumulative incidence of farmwork-related injury during the previous year was 10.5%. We found that depressive symptoms (odds ratio, 3.22; 95% confidence interval, 1.04 to 9.99) and the number of hours working with animals (odds ratio, 2.14; 95% confidence interval, 1.04 to 4.44) were associated with the incidence of farmwork-related injuries.