To determine the use and possible health risks of low-yield cigarettes, we ascertained the cigarette brands and serum thiocyanate (SCN) levels of 2,561 adult smokers (age 25-74) in population-based samples of seven upper Midwestern communities during 1980-82. Brands were coded according to December 1981 Federal Trade Commission (FTC) ratings for "tar", nicotine, and carbon monoxide (CO). Compared to 1980 data from the National Center for Health Statistics for the United States as a whole, a greater proportion of smokers in these communities smoked low-yield brands. More people with higher education than lesser and more women than men smoked low-yield cigarettes. Greater proportions of older people (65-75 years) than younger people (less than 65 years) smoked cigarettes in the highest and lowest brand yield categories. SCN, adjusted for number of cigarettes smoked and for sex, was only weakly associated with brand ratings for "tar" (r = +.12), nicotine (R = +.11), and CO (r = +.15). Furthermore, the gradient in SCN between lowest and highest quintiles of brand strength was less than 16 per cent--much lower than the 300-500 per cent gradient in smoke components implied by FTC ratings. These data add to the evidence that smoking low-yield cigarettes may not be significantly less hazardous than smoking high-yield brands.