  The ultraviolet resonance wind stellar lines, the nebular optical emission
lines and the higher order terms of the Balmer series and HeI absorption lines
detected in the spectra of NGC 604 are interpreted using evolutionary models
optimized for young star forming regions. The evolutionary state and the
massive stellar content of the region is derived in a self-consistent way.
  The three techniques applied suggest that the central ionizing cluster in NGC
604 is very young, 3 Myr old, and that the stars in the cluster were formed in
an instantaneous burst following a Salpeter or flatter IMF, having stars more
massive that 80 Msol. The stellar cluster is able to provide most of the
ionizing photons needed to photoionize the whole nebula, and the wind power to
form the central shell structure where the cluster core is located. The stellar
cluster is affected by an extinction similar to the average extinction that
affects the ionized gas. The estimated number of massive stars in the cluster
is also in agreement with that derived from previous studies based on the
detection of individual stars. The results that we present here support the use
of these techniques for the interpretation of the integrated light of more
distant star forming regions

Astrophysics