I analyzed the frequency and severity of posterior subcapsular cataracts in 291 patients with various forms of hereditary retinal degeneration, including typical retinitis pigmentosa (rod-cone degeneration), cone-rod degeneration, Usher's syndrome, and choroideremia. The overall frequency of posterior subcapsular cataract was 41%, less than generally thought. Posterior subcapsular cataracts were least common in cone-rod degeneration, and most common in the group with autosomal dominant retinitis pigmentosa. Only in the group with sporadic retinitis pigmentosa was a significant sex preference noted; females were affected more often (P less than or equal to .002). Severity was related to age of the patient and duration of disease in those affected. Posterior subcapsular cataract formation is unlikely to be an intrinsic expression of the various genes of hereditary retinal degeneration.