Pigs were allotted to treatments at the initiation of l-carnitine feeding and remained within the same treatment groups for the duration of the experiment. Two pens within the same treatment (50 mg/kg l-carnitine and 5 mg/kg RAC) were removed from the experiment because of clinical ileitis. During the initial period or 33 to 74 kg when graded levels of l-carnitine were fed, there were no differences in growth performance (Table 2). There were no RAC × l-carnitine interactions for ADG, ADFI, or G:F during the last 4 wk of the experiment (Table 3). Increasing RAC increased (quadratic, P < 0.02) ADG and G:F. Average daily gain of pigs fed 5 mg/kg RAC was similar to that of control pigs, but ADG increased and was greatest for pigs fed 10 mg/kg RAC. Gain:feed increased with increasing RAC and was greatest for pigs fed 10 mg/kg RAC. Pigs fed 25 mg/kg l-carnitine had decreased (quadratic, P < 0.06) ADG and ADFI compared with pigs fed 0 or 50 mg/kg l-carnitine.