We analyse the stellar content of a large number of HII galaxies based on the continuum and absorption features of their spectra using population synthesis methods, in order to gain information about the star formation histories of these objects. We find that all galaxies of our sample contain an old stellar population (≥1 Gyr) that dominates the stellar mass, and in a great majority of these, we also found evidence for an intermediate-age population ≥100 Myr apart from the presently bursting, ionizing young generation ≤107 yrs.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html