The purpose was to study the effects of skipping rate on energy expenditure and sex differences in response to rope skipping. Responses of 19 males and 11 females were measured while skipping for 5 min at 125, 135 and 145 skips . min-1. Expired air was routed through a hollow handle to collection bags to provide uninterrupted exercise. Values at the respective rates for the total sample were: VO2 (l . min-1) 2.79, 2.83, 2.85; VO2 (ml . kg-1 . min-1) 41.1, 42.0 42.5; HR (beats . min-1) 176, 177, 177; VE (l . min) 102.2, 103.5, 106.3; R 1.09, 1.07, 1.05; energy expenditure (kj . min-1) 58.6, 59.4, 60.3. Sex differences were found in that females had significantly lower VO2 both in l . min-1 and ml . kg-1 . min-1 but higher HR values than males. Comparison of VO2 values of the females to VO2max values reported for females in the literature suggested that they may have been exercising close to their maximum. There were no differences in any of the values due to skipping rate nor was there interaction between sex and rate. Retrospective cinematographic analysis on two subjects suggested that the failure to find significant differences due to rate may be due to a decrease in vertical displacement resulting in a relatively constant work output as skipping rate increased. Average MET values at the different rates ranged from 11.7 to 12.5, which supported findings from other studies that rope skipping is very strenuous exercise.