Abstract: The results of detecting E rosette function and serum E rosette inhibitory factor(RIF)in 51 cases of psoriasis vulgaris showed that EtRFC decreased markedly in patients in progressive phase, whereas, there was no significant difference in inactive phase as compared with the normal group. The deficiency of E rosette function was related to the activity of the disease: The positive rate of RIF in patients in progressive phase was 60% and was much higher than that of the normal group. With remission of skin lesions E rosette function restored and RIF returned to negative. Suppression of E rosette function could be reversed by short term in vitro preincubatioa of patient's lymphocytes with ConA, which indicated that the decrease of EtRFC in the disease was caused by the defect of their function rather than the reduction of the number of T lymphocyte. Besides RIF. the effect of other inhibitory factors on E resette function on psoriasis should also be considered.