Abstract: Observation on the surfaces of 4 cases of seborrheic keratosis and twelve kinds of other skin diseases with SEM.Lots of round and oval spores abou 3.3-8.3 in diameter were found solely on the horny layer of seborrheic keratosis.Most of them had smooth surfaces.A few spores appeared budding.No mycelium was found.These spores appeared to be pifyrosporum.ovale.There were some scattered and shortened projections on a few spore,surfaces.It seemed that the,pityrosporum ovale has,infrequent secretions with small amount of substance secreted.No,spores were found in 3 cases of papillomatous skin disease.The authors suggested that excess of sebeum might be a favorite environment for teh growth of this bacterium.