A 1% carrageenan solution was injected into the palatal mucosa of male guinea pigs between the two first molars. Biopsy specimens were taken 1, 3, 6, 12 and 24 hours after the injection. Control specimens with healthy mucosa and tyrode injected mucosa were used in order to evaluate the carrageenan-induced inflammation. An intense inflammatory reaction occurred within hours after the carrageenan solution injection. The palatal epithelium exhibited a considerable increase in the number of binucleate cells (P less than 0.001). As proposed by several authors, the inflammation of the underlying connective tissue might explain this phenomenon. The presence of binucleate cells would be an indication that the migration of epidermal cells from the basal to the horny layer proceeds in a hasty and immature fashion.