Of 52 patients (39 women and 13 men; mean age, 65 years) with idiopathic macular cysts or holes, 17 had bilateral involvement. During a mean follow-up period of 28 months, 50% of the macular cysts progressed to holes. Eight of nine eyes with cysts and visual acuities of 6/15 (20/50) or worse at the initial examination developed holes. No holes developed in eyes that had not had cysts at the initial examination. This demonstrated the importance of examining the fellow eye when making a prognosis. Posterior vitreous detachment was present in all the eyes with macular holes and absent in all the eyes with macular cysts at the initial examination. Whenever a cyst progressed to a hole, posterior vitreous detachment also developed. Twenty-five patients had systemic hypertension, 31 had undergone a hysterectomy, taken systemic estrogen, or both, three had adult-onset diabetes mellitus, and 12 smoked cigarettes.