The clinical characteristics of 75 eyes with congenital pits of the optic nerve head were reviewed, particularly in relation to associated serous retinal detachment. Retinal detachment was found in 52% of all eyes with pits and 63% of eyes with temporally located pits. Of 20 untreated eyes with a pit and coexistent macular retinal detachment followed for more than one year, 55% (11/20) had visual acuity less than or equal to 6/30 and 75% (15/20) had subretinal fluid at the most recent visit. Visual fields and intravenous fluorescein angiographic characteristics of pits are discussed and clinical evidence is presented supporting the theory that the associated subretinal fluid is derived from liquified vitreous.