Eight patients were studied to determine the possible use of clofazimine for treating erythema dyschromicum perstans (EDP). The T-helper/T-suppressor cytotoxic ratio (CD-4/CD-8) and the in vitro lymphoproliferative response on stimulation with phytohemaglutin (PHA) and concanavalin A (Con A) were determined in peripheral blood before and after treatment. Of the eight patients studied, seven had excellent to good responses, whereas only one had a marginal response. The immunologic evaluation before and after treatment showed a significant change in the CD-4/CD-8 ratio, a decrease of the response to PHA, and no change in the response to Con A. The results obtained show that clofazimine is useful for treating this nosologic entity because of its cosmetic effect, and also because it induces changes in cell-mediated response, which could be very important therapeutically.