Four types of autosomal dominant retinitis pigmentosa (RP) were discernible in 84 patients by clinical, electrophysiologic, and psychophysical criteria. Type 1 patients showed diffuse fundus pigmentary changes and nondetectable electroretinographic (ERG) cone and rod functions. Both type 2 and type 3 patients showed fundus pigmentary changes more apparent within the inferior retina. Type 2 patients showed marked loss in rod ERG function, with prolonged cone implicit times, whereas type 3 patients showed substantial rod function and normal cone implicit times. Type 4 patients had a funduscopically and functionally "delimited" disease, with substantial cone and rod ERG amplitudes and normal implicit times. The classification of dominantly inherited RP is important for studies of natural history in disease progression, for patient counseling, and for various laboratory investigations of patients with RP in which patient homogeneity should be maximized.