A posterior fundus examination around the macula was performed for the patients diagnosed spontaneous posterior vitreous separation. Of 898 eyes, 358 eyes had epiretinal membranes. The presence of membranes did not correlate to sex. The 2-fold greater incidence was observed in the aged group and emmetropic patients. For the progression, age, sex or refractive error alone was not significant, while aged, emmetropic patients showed greater incidence. The longer duration of the membrane existence also indicated the greater progression.