The galactic giant HII region NGC 3603.

CCD UBV photometry of the ionizing cluster of NGC 3603 has been obtained with the purpose of clarifying the controversy about the distance to the cluster and deriving the age of the system. A distance modulus of (m-M)o = 14.3 and a range of ages for the cluster stars are found which seem to be real and not due to observational error. The average age of the cluster is between 2 and 3 Myr, with a real spread of up to about + or - 2 Myr that is compatible with the dynamical time scale of the cluster. It is shown that star formation is an ongoing process in NGC 3603 that has apparently propagated from the north of the complex toward the giant molecular cloud that borders the starburst cluster. The global properties of the nebula are confronted with those of giant extragalactic H II regions. It is found that the nebular diameter and luminosity agree very well with the value expected on the basis of the observed turbulent velocity.