Mainstream (MS) smoke acetaldehyde (AA), carbon monoxide (CO), and "tar" yields and percentage total reducing sugars in the tobacco blends from a Philip Morris USA database of a large number of commercial U.S. cigarettes were analyzed. MS smoke acetaldehyde is significantly correlated with "tar" yield and also with MS smoke carbon monoxide. These correlations are consistent with recently available data, including the 1999 Massachusetts Benchmark Study. MS smoke acetaldehyde yield is not correlated with reducing sugar (RS) concentration in the tobacco blend. For the available data over the time period 1985-1993, the concentration of reducing sugars (mean values for the brands tested) decreased. The correlations found between MS smoke acetaldehyde yield and "tar" and MS smoke carbon monoxide, and the percentage of the variance in AA yield explained by "tar" and MS smoke CO, coupled with the lack of correlation between "tar" normalized MS smoke AA and RS, plus related pyrolysis studies, support the hypothesis that MS smoke acetaldehyde yields are affected more by cigarette design characteristics influencing total smoke production than by tobacco reducing sugars.