To characterize the effects on guinea pigs of a subchronic exposure to cotton dust at a concentration which caused no acute ventilatory effects, 30 guinea pigs were exposed to 1.6 mg/m³ cotton dust 1182 for 6 hrs/day, 5 days/week for 12 weeks. No effects were seen in breathing rate or respiratory volume over the 12 week period. However, other effects were noted. The rate of weight gain of the exposed animals was found to be decreased when compared with that of a group of 20 sham-exposed animals. Six exposed animals produced antibodies reactive with a cotton dust extract. These results indicate effects were noted in the absence of changes in acute pulmonary function.