  RHII and starbursts are both powered by massive stars. They are the main
contributors to the heating of the ISM via radiative and mechanical energy.
Techniques to derive the stellar content and the evolutionary state of RHIIs
and starbursts from their ultraviolet and optical integrated light are
reviewed. A prototypical RHII (NGC 604) and nuclear starburst (NGC 7714) are
discussed in more detail. The results reveal the necessity of multiwavelength
analyses of these objects to estimate their stellar content and their
evolutionary state in a consistent way.
