Thirty-eight patients with ocular hypertension or glaucoma were treated with topical timolol for 12-30 months (mean 20). A long lasting hypotensive effect of timolol eyedrops was found. However a need to increase therapy during the follow-up period was noted especially in the glaucoma group. Eyes with pseudoexfoliations often required concomitant therapy from the beginning. Ocular side effects were relatively few but four cases of punctate keratitis and another two with decreased corneal sensitivity were observed.