Age is associated with increased deposition of visceral adipose tissue. We examined whether this age-related change in regional adipose tissue distribution had an impact on low-density lipoprotein (LDL) particle size. For this purpose, the plasma lipoprotein-lipid profile, including LDL peak particle diameter as determined by gradient gel electrophoresis, was assessed in 38 young men (aged 26.4 +/- 4.2 years, mean +/- SD) and compared with 40 middle-aged men (55.9 +/- 6.2 years). Middle-aged men had higher values for total body fat and visceral adipose tissue area as measured by computed tomography than young men (P < .001). Although significant differences were noted between the two age groups for plasma cholesterol, triglyceride (TG), apolipoprotein B (apo B), LDL cholesterol, and LDL apo B, as well as the cholesterol to high-density lipoprotein (HDL) cholesterol ratio (P < .001), no difference was found for LDL peak particle size between young and middle-aged men. While visceral adipose tissue was a significant correlate of plasma lipoprotein levels, the fasting TG concentration was the best predictor of LDL particle size, and the regression of TG levels on LDL peak particle diameter was not different between the two age groups. These results suggest that middle-aged men are characterized by an increased concentration of LDL particles (reflected by increased LDL apo B levels) but not by a reduced LDL peak particle size compared with young men. It is therefore proposed that in the absence of an important age-related change in TG levels, age per se is associated with an increased concentration of atherogenic LDL particles rather than a reduction of LDL particle diameter.