Colchicine inhibits processes known to be involved in the pathogenesis of peritoneal adhesions. Daily administration of 50 micrograms of colchicine to 22 rats significantly diminished adhesion formation, as compared with dexamethasone-treated and untreated rats. Rats that developed at least three adhesions of grade 3 (scale 0 to 4) were strikingly less prevalent among the colchicine-treated animals than the untreated group (9.1% versus 40.9%, P less than 0.001). The double product of the number and grading of adhesions was significantly lower (P less than 0.05) in the colchicine group. Colchicine is more effective than dexamethasone in inhibiting adhesion formation in the rat.