Serum ApoB-AGE (A) and total serum protein-AGE levels (B) were measured in healthy nondiabetic smokers and healthy, nondiabetic nonsmokers. AGE-ApoB levels in smokers (mean ± SD, 247 ± 76 units/ml, n = 17) were significantly higher (P = 0.018, unpaired Student t test) than nonsmokers (mean ± SD, 190 ± 54, n = 17). Serum AGE levels in smokers (210 ± 51 AGE units/ml, n = 17) were significantly higher (P = 0.01) than the serum-AGE levels in nonsmokers (161 ± 53 AGE units/ml, n = 17). AGE units are expressed relative to an ApoB-AGE standard (1 unit = 1 ng of ApoB, ICN Pharmaceuticals, Biochemical Division, Aurora, OH) and a BSA-AGE standard in the respective assays. Subjects were not controlled for age, sex, or number of pack-years smoked.