Ten-year results are reported from a randomised controlled trial of anti-smoking advice in 1445 male smokers, aged 40-59, at high risk of cardiorespiratory disease. After one year reported cigarette consumption in the intervention group (714 men) was one-quarter that of the "normal care" group (731 men); over 10 years the net reported reduction averaged 53%. The intervention group experienced less nasal obstruction, cough, dyspnoea, and loss of ventilatory function. Over 10 years their mortality from coronary heart disease was 18% lower than controls (49 and 62 deaths), and that for lung cancer was 23% lower (18 and 24 deaths). Deaths from non-lung cancers were higher in the intervention group (28 v 12 deaths). This unexpected difference was due about equally to an excess in intervention and a deficiency in normal care men, it showed no site specificity, and it was unrelated to change in smoking habit. These findings suggest that it is more likely to have been due to change than to intervention. The total number of deaths were 123 in the intervention group and 128 in normal care (95% confidence limits of difference -22% to +23%). The policy of encouraging smokers to give up the habit should not be changed.