To determine the effects of testosterone (T) on lipid assimilation in different adipose tissue depots, T (250 mg, im) was given to 17 middle-aged men 5 days before abdominal surgery. Twenty-four hours before surgery, 10 microCi labeled oleic acid in 80 g milk fat were administered orally. Lipid radioactivity was measured in adipose tissue biopsies from abdominal ac, omental, and retroperitoneal adipose tissues. Subcutaneous, visceral (omental plus mesenteric), and retroperitoneal adipose tissue masses were determined using computerized tomography scans at 22 levels. Sixteen men who were not treated with T served as controls. T administration was followed by an increase in serum concentrations from 17.7 +/- 1.1 to 32.6 +/- 1.8 nmol/L (P < 0.001) and a marked (> 50%) reduction compared with controls in lipid radioactivity in omental and retroperitoneal adipose tissues, but not in sc adipose tissue. In controls, sc, visceral, and retroperitoneal adipose tissues assimilated 59.2 g (73.4%), 16.9 g (20.9%), and 4.6 g (5.7%), respectively, of the orally administered fat. In the T-treated men, this was changed to 73.5 g (88.8%), 6.4 g (7.7%), and 2.9 g (3.5%), respectively. It was concluded that T inhibits triglyceride assimilation in intra-abdominal depots and apparently directs this lipid to sc fat in men.