The association between blood pressure treatment, blood pressure level and mortality, taking other cardiovascular risk factors into account was studied. A 12-year follow-up of a cardiovascular risk factor screening performed by the Oslo study group in Oslo and by ambulatory teams from the National Health Screening Survey in three counties in Norway was done. All men in Oslo and all men and women in the three counties, (age 40-49) participated, of these 33154 men and 16407 women have complete data on blood pressure and treatment, including subjects reporting previous myocardial infarction or stroke. Mortality from coronary heart disease, stroke and all causes by blood pressure treatment and blood pressure level were studied. At the initial screening 1058 men and 817 women reported taking blood pressure medication, of which 201 and 41 died during follow-up. Total number of deaths were 2341 in men and 421 in women, of these 131 deaths in men and 47 in women reporting previous infarction or stroke. Those reporting blood pressure treatment had a marked excess mortality from cardiovascular disease and all causes of death. A J-shaped association between blood pressure and mortality was marked in the treated group, but weak in those not on treatment. It is concluded that blood pressure treatment is associated with excess mortality from all causes. This may indicate that "real life" treatment outcomes are inferior to those reported from controlled clinical trials. There is a J-shaped association between all cause mortality and blood pressure in men on treatment.