Ten sets of five littermate pigs with a high genetic capacity for lean tissue growth (350 to 370 g/day) and reared via a segregated-early-weaning scheme were used to determine the dietary thiamin needs of pigs exhibiting a high rate of lean tissue growth. Within each litter, pigs were randomly allotted to one of five dietary thiamin concentrations equivalent to 200, 330, 460, 590, and 720% of the current NRC (1988) estimated requirement for 11 to 22 pound pigs. Pigs were penned individually and given ad libitum access to experimental diets and water from 22 to 88 pounds body weight (BW). Pooled across diets, the pigs’ body weight gains and feed:gain ratios averaged 1.70 pounds per day and 1.44 pounds, respectively, from 22 to 88 pounds body weight. Dietary thiamin concentration did not alter daily feed intake, rate of body weight gain, or feed:gain ratios. Based on these data, dietary thiamin in a corn-soy-based diet (2.2 ppm) is adequate for optimal rate and efficiency of gain in high lean growth pigs from 22 to 88 pounds body weight.