Individuals with developmental disability have historically demonstrated lower levels of physical fitness than their non-disabled counterparts. In addition, adolescents and young adults with Down syndrome generally display lower levels of fitness than peers with other developmental disabilities. Research posits numerous reasons for these discrepancies, including physiological dysfunction, neurological lesion, delayed growth and development, inadequate communication skills, lack of motivation and an inability to understand the abstract implications of exercise and life-long fitness. The purpose of this study was to determine the effects of verbal encouragement on performance and perceptual responses during a graded exercise test to exhaustion. Sixteen subjects with developmental disabilities (M age=18, M IQ=54), eight with Down syndrome, were selected for participation. Subjects performed two graded exercise tests (Bruce protocol) on two separate occasions in counterbalanced sequence. During one test, consistent verbal encouragement was given by the investigative team throughout the exercise protocol. The alternate test included no verbal encouragement. Heart rate (HR) and perceived exertion(RPE) were recorded during each workload. Both tests were terminated at volitional exhaustion. Prior to testing, subjects were given a thorough orientation to the exercise protocols on the treadmill, including instruction on the use of the Children’s OMNI scale of perceived exertion (Robertson et al., 2000). Time to exhaustion, peak heart rate response and submaximal perceptual responses were compared both between conditions and between groups (Down vs. non-Down). Two-way analyses of variance with repeated-measures revealed significantly longer (p<.01) times to exhaustion (8:55 vs. 7:50) and greater peak HR (174 vs. 163 b/min) for the verbal encouragement trials. The non-Down group achieved significantly (p<.05) longer times to exhaustion (8:52 vs. 6:49), however, peak HR was similar (166 vs. 161) between groups. No significant differences were observed for HR and RPE at given submaximal workloads as a function of verbal encouragement or group category. It was concluded that verbal encouragement is of prime importance in eliciting higher levels of work performance in persons with developmental disabilities. This may be particularly important for individuals with Down syndrome given their generally lower levels of fitness. It does not appear, however, that verbal encouragement alters perceptions of effort during submaximal exercise in persons with developmental disabilities.