The aim of this study was to compare the power outputs of the intermittent critical power (CPi) with the intermittent maximal lactate steady state (MLSSi) and to compare the physiological and perceptual responses exercising at CPi and MLSSi. Ten subjects performed intermittent trials on a cycle ergometer to determine CPi and MLSSi using 30:30 seconds of effort and pause. The oxygen uptake (&OV0312;o2), heart rate (HR), blood lactate concentration ([Lac]), and rating of perceived exertion (RPE) responses were compared during 30-minute cycling at CPi and MLSSi. The CPi (267 ± 45 W) was similar to MLSSi (254 ± 39 W), and they were correlated (r = 0.88; p < 0.05). The &OV0312;o2 and HR responses stabilized throughout exercising at CPi (2.52 ± 0.52 L·min; 156 ± 8 b·min) and MLSSi (2.41 ± 0.32 L·min; 152 ± 10 b·min). These physiological variables were similar between conditions. However, the [Lac] and RPE were higher from the middle to the end of exercise duration at CPi ([Lac] = 6.9 ± 2.6 mM; RPE = 17.1 ± 2.1 a.u.) compared to MLSSi ([Lac] = 5.1 ± 0.9 mM; RPE = 15.7 ± 1.8 a.u.). Therefore, CPi intensity determined from 30:30 seconds of effort and rest periods on a cycle ergometer is equivalent to the MLSSi, and there is a physiological steady state throughout both exercise intensities, although the [Lac] and RPE responses at CPi are higher than at MLSSi. Thus, the CPi and MLSSi may be used as tools for intermittent training evaluation and prescription.