The incidence of acute closed-angle glaucoma was studied in 1796 patients derived from the hospital discharge registry of Finland for the years 1973–1982 (469 males and 1327 females). The average incidence was 3.8 cases/100 000 per year. The incidence showed a steep rise with age. The highest incidence was observed in both sexes in the group 80 years of age and older. The incidence was higher (Chi-square 7.81,df = 1,P < 0.01) among women (5.3/100 000 per year) than among men (2.0/100 000 per year). The age-adjusted incidence for the whole period of 1973–1982 showed no statistically significant rise. The seasonal variation of incidence was statistically significant (P < 0.001). In winter (December, January, February) and in autumn (September, October, November) the incidences were higher compared to spring (March, April, May) and summer (June, July, August). This association was greater (P < 0.001) among females than among males (P < 0.05). Mean sunshine hours showed a reverse association with the incidence of acute glaucoma. The association was statistically significant when both sexes were pooled together (P < 0.001). There was no sex interaction with regard to the association of incidence of acute glaucoma and mean sunshine hours.