in the reported experiments, twenty-six volunteers with normal pulmonary function were exposed to cotton dust in a model card room $left double quote$ standard $right double quote$ cotton was harvested and prepared for carding in the usual manner. $left double quote$ closed-boll $right double quote$ (cb) cotton was harvested before the bolls had opened; the bolls were washed in a 0 5 sodium hypochlorite solution and then allowed to open under controlled conditions. bract was manually removed prior to opening on one-half of this cotton. results were analyzed for statistical significance. forced expiratory volume in one second (fev//1) rose slightly over the day with no exposure and fell slightly after rayon standard cotton exposure. both changes were significantly different from the average fall of 5 after standard cotton exposure mississippi cb cotton, with or without bract, and texas cb cotton without bract caused significantly smaller declines in fev//1 than standard cotton. in normal volunteers, airway response is less to dust from closed-boll cotton without bract than to standard cotton dust. 13 refs