OBJECTIVE To determine whether the calf:brachial ratio for systolic blood pressure is reduced in both current and ex-smokers of cigarettes. METHODS Cross-sectional study of the calf:brachial systolic blood pressure ratio and smoking history. METHODS Four hundred and ten male and 138 female civil servants aged 35-59 years working in the Department of the Environment Building, London. RESULTS In men the systolic blood pressure ratio (Doppler calf:auscultatory brachial) decreased above the age of 50 years. However, different patterns were observed in those who had smoked at some time and those who had never smoked. In those who had never smoked the ratio in men aged 35-44 years was lower than that in men aged 55-59 years. In those who had smoked the average ratio rose from the age of 35-44 years to the age of 45-49 years and then fell to below the former value at the age of 55-59 years. There was a significant difference between lifelong non-smokers and current smokers at age 55-59 years. The pattern was similar in both male ex- and current smokers, and ex-smokers had results intermediate between those for current smokers and those who had never smoked. In women who had never smoked the ratio increased from the age of 35-44 years to the age of 50-59 years. In women aged 50-59 who currently smoke or used to smoke cigarettes the average ratio was close to that for women aged 35-44 years who had never smoked. CONCLUSIONS The calf:brachial systolic blood pressure ratio is a simple measurement that may prove useful in detecting the early adverse effects of smoking on peripheral vascular disease. Lower ratios at older ages occurred in both current and ex-smokers, and the effects of smoking on peripheral arterial disease may not be easily reversible at older ages.