Objective To investigate the role of skin homing T lymphocytes in the development of psoriasis vulgaris(PV). Methods Indirect immunofluorescent double staining technique was employed to study the expression of infiltrating skin homing T lymphocytes in normal, uninvolved perilesional and lesional psoriatic skin in different stages (progressing, stable or regressing) and in normal human skin. Results ①Expression of cutaneous lymphocyte associated antigen (CLA) was found in the majority of CD3+T lymphocytes in normal human skin and in lesions of PV, and CD45RO phenotype was expressed in almost all CLA+T lymphocytes. ②In psoriatic lesions, the number of CD4+CLA+and CD8+CLA+cells was higher in progressive stage than that in stable stage(P