This study compared cardio-respiratory responses during maximal arm work using a Monarch Model 880 Rehab Trainer to cardio-respiratory responses during maximal leg work on a Monarch Model 850 Bicycle Ergometer. Subjects for the investigation were 17 male university students ranging from 18 to 28 years of age. The specific variables compared included submaximal and maximal heart rate, maximum oxygen consumption, maximum oxygen pulse, pulmonary ventilation, ventilatory equivalent, and mean recovery heart rate. Each subject was tested during arm and bike work. A repeated analysis of variance indicated significantly higher values for maximum oxygen consumption, maximum pulmonary ventilation, maximum oxygen pulse, and maximum heart rate during bicycle ergometry. The ventilatory equivalent was significantly lower during bike work while the mean recovery heart rate during arm work was significantly lower than during bike work. There was no significant difference in submaximal heart rates between the groups. Reasons for the results are discussed. (JD)