Upper panels: expected number of Wolf-Rayet stars (dashed lines) and of RSGs in a coeval population (continuous lines) of 10 000 stars. Models with initial masses of between 9 and 25  M_⊙ computed with different mass-loss rates during the RSG phases give the different continuous lines labeled by the enhancement factor considered for the mass-loss rate during the RSG phase. The populations of WR stars are very little affected by these changes of mass-loss recipes (see text). Lower panels: fraction between the number of RSG and the number of main-sequence stars two magnitudes below the turn-off. The black and empty squares correspond to observed ratios in stellar clusters with between 20 and 50 stars and with fewer than 20 stars. From left to right, the points correspond to the following clusters: NGC 1976, NGC 6231, NGC 884+4755, NGC 457, and NGC 581+2439 (see Meynet et al. 1993).