Lipoprotein (a) (Lp (a)) was determined in 1527 individuals participating in the Northern Sweden WHO MONICA project for monitoring of cardiovascular risk factors in the general population. Subjects were randomly selected and stratified according to sex and age. A weak but significant relation between Lp (a) and increasing age was found in both sexes (p < 0.01). Menopausal status was the strongest independent predictor of Lp (a) level in women (p = 0.010). Fibrinogen was independently related to Lp (a) in both men and women (p < 0.05). An inverse relation between waist-to-hip ratio and Lp (a) was found in men (p < 0.01). Hypertensive subjects treated with diuretics had significantly higher Lp (a) than hypertensives on other agents (p < 0.05). Only a minor proportion of Lp (a) variance could be explained by lifestyle factors, which supports the contention that genetic factors primarily control Lp(a) level.