THE POPULATION OF MASSIVE STARS IN R136 FROM HST FOC UV OBSERVATIONS/

New ultraviolet (lambda congruent-to 1300 A, lambda congruent-to 3400 A), HST FOC observations have been used to derive the UV color-magnitu de diagram (CMD) of R136, with the main scientific goal of studying th e upper end of the stellar mass function at ultraviolet wavelengths wh ere the color degeneracy encountered in visual CMDs is less severe. Th e CMD has been compared to a set of theoretical isochrones, which have been computed using the latest generation of evolutionary models and model atmospheres for early type stars. Wolf-Rayet stars are included. Comparison of the theoretical and observed CMD suggests that there ar e no stars brighter than M130 congruent-to 11. We use the observed mai n sequence turn-off and the known spectroscopic properties of the stel lar population to derive constraints on the most probable age of R136. The presence of WNL stars and the lack of red supergiants suggests a most likely age of 3 +/- 1 Myr. A theoretical isochrone of 3 +/- 1 Myr is consistent with the observed stellar content of R136 if the most m assive stars have initial masses around congruent-to 50 M..