The combined effects of a high-fat-supplemented diet and exercise training on serum lipids as well as on lipoprotein lipase activity in white and brown adipose tissues of the rat were evaluated. Male Wistar rats were fed ad libitum either a stock diet or the stock diet supplemented with food items rich in fat. Half of each dietary group was submitted to daily treadmill running for 35 days. Food intake and final body weight were raised by the high-fat-supplemented diet and lowered by exercise training. Postprandial serum triglycerides were not affected by diet or exercise, whereas the latter decreased total cholesterol in the high-fat group only (14%, P less than 0.01). Total lipoprotein lipase activity in white adipose tissue was elevated (120%, P less than 0.01) by high-fat feeding, and this increase was greatly reduced by concomitant exercise training. In brown adipose tissue, however, the large elevation (104%, P less than 0.01) in enzyme activity brought by the high-fat diet was unaltered by concomitant training. Thus a high-fat-supplemented diet increased lipoprotein lipase activity in both an energy-storing and a heat-producing tissue, and exercise training was able to counteract this effect in white, but not in brown, adipose tissue. These findings support the notion that the regulation of lipoprotein lipase is tissue specific.