Abstract: Twenty cases of psoriasis vulgaris in their progressive, static and regressive stages were observed by electron microscopy, Control skin samples were taken from three healthy persons and from thcee psotiatics whose skin appeared normal clinically, In the progressive and static cases, it was found that there were extensive deposits in the intercellular spaces of stratum corneum, and in the stratum spinulosum, there was increase in cell volume and with increase in size and number of the nuclei. The tonofibrils in cyfoplasms decreased, rough suifaced endoplasmic reticulum and ribosomes increased, the mitochondria increased and degenerated. The Golgi complex are well developed, the changes of the keratinocytes are characterized by widening of intercellular space and the decrease in the number of desmosomes.The regressive stage of psoriasis vulgaris (that is, the skin lesions disappeared' entirely) the electron microscopy is almost normal. But帅ile the skin lesions of the disease existed, that is to say, during, progressive and static stages, the clinically and macroscopically normal skins showed the change of psariasis vulgaris, under electron microscope.