Résumé : The mitogenic response of human lymphocytes and the short-lived suppressor cell function on concanavalin A response were studied as dependent variables in 194 patients using multiple regression analysis, with health status and sex as dummy variables, and age as an explicative one. This study confirms a decrease of the lymphocyte functional response to mitogens with aging. A sex-related defect in suppressor cell function is put forward in females independently of age. An inverse linear relationship is found between the functional response to pokeweed mitogen (T and B mitogen) and suppressor cell function in males but not in females. No such relationship is found with the pure T mitogens (Con A and phytohemagglutinin-A). The present study suggests that a defect in short-lived suppressor cells can play some role in the greater incidence and prevalence of autoimmune diseases in women while the depressed lymphocyte response of old people cannot be explained by modifications of the activity of these suppressor cells. ? 1987.