On group of 20 guinea pigs was exposed to cotton dust at 21 mg/m³, 6 hours/day, 5 days/week for 52 weeks. A similar group was used as a control. Daily measurement of pulmonary function prior to exposure and following exposure were made on all animals. These measurements consisted of tidal volume, measured indirectly as P with whole body plethysmography and of respiratory frequency (f). Both P and f were measured with the animal breathing air or a mixture containing 10% CO₂, 20% O₂, and 70% Ng flowing through the whole body plethysmography. The results indicate that inhalation of cotton dust induced an acute as well as a chronic effect.