In this report, we compare the respiratory health of swine producers, grain farmers, and nonfarming control subjects, separately in all age groups and in young subjects. We examined 249 swine producers (age 37.7 years), 251 grain farmers (age 44.7 years), and 263 nonfarming subjects (age 40.7 years). Swine producers had significantly more symptoms of chronic bronchitis (15.3 percent) than did grain farmers (7.2 percent) or nonfarming men (5.7 percent). After controlling for age, height, and smoking, the functional indices of airflow (FEV1, FEV1/FVC, FEF25-75, Vmax50, and Vmax25) were slightly but significantly lower in swine producers than in grain farmers. In comparison with nonfarming subjects, swine producers also had significantly lower FEV1/FVC, FEF25-75, and Vmax50. Respiratory symptoms were associated with the number of hours of work per day. This indirect index of exposure was also inversely associated with FVC (p < 0.01) and FEV1 (p = 0.06), after adjustment for age, height, smoking, and dust mask usage. A relative excess of respiratory symptoms and lower lung function variables were found in swine producers aged 26 to 35 years. Also in this age group, a multivariate analysis revealed statistically significant effects of daily duration of work on FVC and FEV1. The results confirm that working in swine confinement units is a risk factor for chronic respiratory symptoms and minor lung function changes. An increased risk in young workers may reflect more intense occupational exposure in this subgroup of swine producers.