Data on 144 patients who in 1969-1973 were found to have ocular hypertension greater than or equal to 25 mmHg without glaucomatous damage were collected retrospectively. Intraocular pressure-lowering treatment was prescribed with few exceptions. Thirteen out of 37 patients (35%) with exfoliation syndrome developed glaucomatous damage during the follow-up periods ranging from 5 to 14 years (mean 9.4 years). The corresponding result for patients without exfoliation syndrome was 20 out of 111 subjects (18%, mean follow-up 11.7 years, range 5-15 years). Low average intraocular pressure during the follow-up seemed to prevent the eyes from developing glaucomatous damage. This was especially evident for eyes with the exfoliation syndrome. The long-term effect of medical therapy on the pressure level of hypertensive eyes was often negligible.