Studies of the pharmacological activity of cotton dust aqueous extract (CDE), following various solvent and chemical treatments, on the rat stomach fundus (RF) strip revealed that there is more than one RF-contractor agent present. Solvent extraction studies confirm that there is a highly hydrophillic rat fundus contractor agent which is not soluble in absolute ethanol, ether or dry 1,4-dioxan. The major contractor agent was shown to be susceptible to base hydrolysis whilst being relatively stable to boiling in aqueous solution for short periods and to acid hydrolysis. The RF activity of CDE was also found to be stable to iodine and to catalytic low pressure hydrogenation. The major part of the activity could be abolished by selective oxidation of 1,2-diols.