The effects of carteolol hydrochloride on visual function in normal-tension glaucoma (NTG) were investigated. 22eyes of NTG patients were divided into two groups, i.e., (1) a group receiving topical application of 2% carteolol hydrochloride b.i.d. and 2 an unmedicated group. During a 18 month period, intraocular pressure and visual field (measured by Humphrey automated perimetry) were measured every 3 months, and the measurements obtained in the two groups were compared. Analysis of the results revealed a considerable reduction in intraocular pressure in the carteolol group as compared with the control group. The progression of mean deviation tended to be less in the carteolol group, but the intergroup difference in this respect was not statistically significant. However, increase in corrected pattern standard deviation was clearly less pronounced in the carteolol group than in the control group. These results supported the conclusion that carteolol is effective in inhibiting deterioration of the local visual field. This is attributed to increased ocular perfusion due to diminished intraocular pressure, as well as an inhibitory effect upon vasoconstriction in the optic nerve head due to intrinsic sympathomimetic activity, preventing decrease in papillary blood flow and adverse effects upon ocular circulation.