The purpose was to compare heart rates and completion times of adults with MR after performing a 1-mi walk test with and without a pacer. Fifteen participants (8 males, 7 females) with mild or moderate mental retardation (M age = 38.8 years ± 10.2) performed the test a minimum of two times with a pacer and two times without a pacer. Analysis of variance revealed no significant difference between genders; thus data were combined for further analysis. Intraclass reliability coefficients (R) for walk time with a pacer, walk time without a pacer, heart rate with a pacer, and heart rate without a pacer were .99, .99, .91, and .95, respectively. Results indicated that the average walk times for the pacer and no pacer conditions were significantly different, t (14) = 3.11, p = .008. The pacer condition resulted in a faster average walk time by approximately 1 min; however, there was no significant difference between conditions on heart rate. Therefore, it is recommended that, when having adults with MR perform a walk test, a pacer should be used to assure maximum performance.