We tested the ability of aqueous extracts from several varieties of cotton bracts to: 1) contract isolated canine airways, and 2) cause 5-HT release from human platelets. With regard to airway contractions, the order of effectiveness was: Lambright GL-4 = Early Cot WR - LX-571 >Acala SJ-2 = Coker 310 green bract; >>Coker 310 brown bracts = 0. With regard to 5-Ht release from platelets, the order of effectiveness was: LX571 = Acala SJ-2 >Lambright GL-4 = Coker 310 green bracts >Early Cot WR >>Coker 310 brown bracts. We conclude that the concentration of the bronchoactive and platelet active factors varies considerably among bracts obtained from different varieties of cotton. Furthermore, bracts containing a high concentration of the bronchoactive factor do not necessarily contain a high concentration of the platelet active factor and vice-versa.