The intraocular pressure reducing effect and side-effects of latanoprost, a phenyl-substituted prostaglandin analogue, were compared with those of timolol, in a group of 31 glaucomatous or ocular hypertensive patients, divided into three subgroups. The study was randomized and double masked. At the end of 6 month's treatment with latanoprost 0.005% once daily, either as a morning dose or as an evening dose, there was a reduction in intraocular pressure of 33% (p