The aim of the study was to evaluate a ramp bicycle ergometer exercise protocol consisting of a very small but rapid increase in load (2 watts/12 seconds) for direct measurement of the VO2 max. Eighteen sedentary healthy subjects were in Group I (16 men, mean age 29 +/- 6 years) and 10 men with chronic stable cardiac failure in Group II (mean age: 51 +/- 16 years). All subjects performed two exercise tests within a period of 8 days, one with a ramp protocol (protocol R) and the other with a standard triangular exercise protocol (protocol T) of 30 watts/3 minutes for Group I and 20 watts/2 minutes for Group II. All procedures were performed until the subjects were exhausted. Direct measurement of VO2 max was performed by rapid response analysers enabling a cycle to cycle study. The parameters were measured and compared by a paired Student t test at each stage of the test: at rest, at submaximal exercise (third level), at anaerobic threshold and at maximal exercise. There was no significant difference between VO2 max and VO2 at the threshold of ventilation between the two populations. An increase in carbon dioxide production at different stages was observed with the ramp protocol. Furthermore, the highest maximal respiratory quotient and anaerobic threshold appeared earlier in Group II with the ramp protocol. Therefore, with respect to the standard triangular protocol, the ramp protocol provides comparable VO2 values. Its potential value, reported in the literature, is a better correlation between the observed and theoretical VO2 values. However, an increase in CO2 production should be underlined, probably related to greater recruitment of anaerobic metabolism in the absence of a steady state. This may be the reason for attaining the anaerobic threshold earlier.