We have measured pokeweed mitogen-induced IgG secretion by peripheral blood mononuclear cells obtained from two different groups of progressive multiple sclerosis (MS) patients. MS patients with chronic progressive active disease (CPMS-A) have higher IgG secretion than stable (burnt-out) patients (CPMS-S). We have also measured suppressor cell function and phenotyped the T helper cells of some CPMS-A patients. This group differed from CPMS-S and from controls: they had high IgG secretion, low suppression and their T helper phenotypes showed a high ratio of T helper/inducers over T suppressor/inducers.