Acid cholesteryl ester hydrolase (CEH) activity was assayed in mononuclear cells of patients with symptomatic atherosclerosis (transient ischemic attacks, TIA) and in age-matched controls showing no evidence of atherosclerosis. The acid CEH level of TIA patients was significantly lower than that of controls (1074 +/- 128 vs 2113 +/- 255 pmol/mg P/hr, mean +/- SE). Neither mononuclear cell nor plasma cholesterol and cholesteryl ester concentrations differed significantly between atherosclerotic and control groups. TIA women had lower mononuclear cell concentrations of free cholesterol than men.