In the present article, three scales developed by Borg are compared on bicycle ergometer work. In the first study, comparing the Borg Ratings of Perceived Exertion (RPE) and Category scales with Ratio properties (CR10) scales, 40 healthy subjects (12 men and eight women for each scale) with a mean age of about 30 years (SD approximately 6) participated. A work-test protocol with step-wise increase of work loads every minute was used (20 W increase for men and 15 W for women). Ratings and heart rates (HRs) were recorded every minute and blood lactates every third minute. Data obtained with the RPE scale were described with linear regressions, with individual correlations of about 0.98. Data obtained with the CR10 scale could also be described by linear regressions, but when described by power functions gave exponents of about 1.2 (SD approximately 0.4) (with one additional constant included in the power function). This was significantly lower than the exponent of between 1.5 and 1.9 that has previously been observed. Mean individual correlations were 0.98. Blood lactate concentration grew with monotonously increasing functions that could be described by power functions with a mean exponent of about 2.6 (SD approximately 0.6) (with two additional constants included in the power functions). In the second study, where also the more recently developed Borg CR100 scale (centiMax) was included, 24 healthy subjects (12 men and 12 women) with a mean age of about 29 years (SD approximately 3) participated in a work test with a step-wise increase of work loads (25 W) every third minute. Ratings and HRs were recorded. RPE values were described by linear regressions with individual correlations of about 0.97. Data from the two CR scales were described by power functions with mean exponents of about 1.4 (SD approximately 0.5) (with a-values in the power functions). Mean individual correlations were about 0.98. In both studies, a tendency for a deviation from linearity between RPE values and HRs was observed. The obtained deviations from what has previously been obtained for work of longer duration (4-6 min) points to a need for standardization of work-test protocols and to the advantage of using CR scales.