The criteria used to establish whether a true maximal test has been attained have been criticised. The aims of this study were: a) to assess the incidence of plateau of VO2max and other criteria in a maximal exercise test in laboratory, and b) to determine if the protocol and ergometer have an influence on these criteria. 135 sportsmen, aged 12-42 years, were examined. Maximal exercise tests were carried out with different ergometer (treadmill vs cycle) and protocol (continuous vs discontinuous) according to the sports discipline. The criteria analysed were: oxygen uptake ,(< 150 mL/min and < 2 mL/kg/min), Respiratory Exchange Ratio (≥ 1,10) and Heart Rate (≥ 95% HRmax). Only 51% of the maximal test analysed reached the plateau of oxygen uptake and 7% did not reached any criteria; the 28% reached three criteria and 70% two. The protocol and ergometer were determinant in the criteria analysed in the maximal exercise tests.