Mental disability, variables associated with it and predictors of mental disability in late life were studied in 716 men from eastern and southwestern Finland in connection with the 25-year follow-up of the east-west study, which formed the Finnish part of the seven-countries study. The examinations were carried out in autumn 1984, when the men were 65-84 years of age. According to a 10-item mental status questionnaire, 95% of the men had normal mental capacities. There were no differences between the 2 areas. Old age, low educational level, low functional capacity, low body mass index, low serum cholesterol, low diastolic blood pressure, low alcohol or coffee consumption, low hemoglobin, low serum calcium, low serum triiodothyronine, high scores on the Zung Self-rating Depression Scale, and presence of transient ischemia or stroke were associated with mental disability in 1984. In the prospective analysis, low forced vital capacity, low forced expiratory volume in 0.75 s and high blood pressure in middle age predicted mental disability in old age.