Data from 2754 cigarette smokers who smoke no other forms of tobacco are extracted from the baseline cross-sectional survey of the Scottish Heart Health Study. Carbon monoxide in expired-air (CO-E), serum thiocynate and serum cotinine measurements from these smokers are compared with the carbon monoxide (CO), nicotine and tar yields of the cigarettes which they smoke, controlling for daily cigarette consumption, the sex of the smoker and the other cigarette yields. CO-E is found to increase positively with CO and tar yield, but inversely with nicotine yield. Thiocyanate increases positively with CO, is not significantly affected by tar, but increases inversely with nicotine. Cotinine is affected only by tar, in a positive direction for women. We conclude that smokers appear to self-titrate their consumption of nicotine by more aggressive smoking of lower-strength cigarettes.