Abstract: Thirty gatients (male 15,female 15) with psoriasis valgaris from outhatient department were investigated by measuring erythrocyte fltcrability (deformability) and ATPase activity of erythrocyte membrane.22 healthy persons (male 10,female 12) served control.It was found that the index of erythrocyte filterability was sisynificantly higher (P<0.001) in the psoriatic group (0.508±0.037) than in that of the control group (0.320±0.023).The Na⁺K⁺ ATPase activity of erythrocyte membrane markedly elevated in the paoriatic group with the course of disease > 1 year (0.704±0.123) compared with the control group (0.421±0.029) or with the psoriatic group with the course of disease < 1 year (0.384±0.070),P<0.05.The Mg⁺⁺ ATPase activity of erythrocyuc membrane reduced in the psoriatic group with the course of disease < 1 year (1.024±0.209) Compared with controt group (1.813±0.138),P<0.05.The results showed that not only the iceratinocytes but also the erythrocytes domonstrated abnormal alterations in patients with psoriasis.