The influence of fullerenol on the activities, of human erythrocyte membrane ATPases and the fluidity of the plasma membrane as well as the possibility of fullerenol incorporation into the plasma membrane, were investigated. Fullerenol at concentrations up to 150μg/mL induced statistically significant decreases in the anisotropy of 1-anilino-8-naphthalene sulfonate (ANS) (14%), N,N,N-trimethyl-4-(6-phenyl-1,3,5,-hexatrien-1-yl)phenylammonium p-toluenesulfonate (TMA-DPH) (7.5%) and 1,6-diphenyl-1,3,5-hexatriene (DPH) (9.5%) after a 1-hour incubation at 37°C. The effect disappeared for ANS and TMA-DPH, but not for DPH, after washing out the fullerenol. Incubation of erythrocyte membranes with fullerenol led to decreases in the activities of Na(+),K(+)-ATPase (to 23% of the control value), Ca(2+)-ATPase (to 16% of control) and Mg(2+)-ATPase (to 22% of control). Washing out the fullerenol lessened the inhibition of the Na(+),K(+)-ATPase (37% of control) and Ca(2+)-ATPase (23.5% of control); however, it did not influence Mg(2+)-ATPase activity. Furthermore, fullerenol could associate with erythrocyte plasma membranes. Our results suggest that fullerenol associates primarily with the surface of the plasma membrane; however, it can also migrate deeper inside the membrane. Moreover, fullerenol influences membrane ATPases so that it may modulate ion transport across membranes.