The clinical characteristics and follow-up changes of 64 patients with solitary congenital hypertrophy of the retinal pigment epithelium were studied. Thirty-five of the patients were followed up for one to 14 years with serial fundus photography. Progressive increase of the hypopigmented part of the lesion was observed in 29 of the 35 patients who were followed up (82.8%). An enlargement of the lesion was seen in 26 of the 35 patients (74.3%). Two additional changes, that is, pigmented areas adjacent to congenital hypertrophy of the retinal pigment epithelium and linear streaks of the pigment epithelium, were documented. Pathogenetic mechanisms for the development of these changes remain unknown.