  We present new near-infrared J and K imaging data for 67 galaxies from the
Universidad Complutense de Madrid survey used to determine the SFR density of
the local universe by Gallego et al. (1995). This is a sample of local
star-forming galaxies with redshift lower than 0.045, and they constitute a
representative subsample of the galaxies in the complete UCM survey. From the
new data, complemented with our own Gunn-r images and long-slit optical
spectroscopy, we have measured integrated K-band luminosities, r-J and J-K
colours, and Halpha luminosities and equivalent widths. Using a maximum
likelihood estimator and a complete set of evolutionary synthesis models, these
observations have allowed us to estimate the strength of the current (or most
recent) burst of star formation, its age, the star-formation rate and the total
stellar mass of the galaxies. An average galaxy in the sample has a stellar
mass of 5E10 Msun and is undergoing (or recently completed) a burst of star
formation involving about 2 per cent of its total stellar mass. We have
identified two separate classes of star-forming galaxies in the UCM sample: low
luminosity, high excitation galaxies (HII-like) and relatively luminous spirals
galaxies (starburst disk-like). The former show higher specific star formation
rates (SFR per unit mass) and burst strengths, and lower stellar masses than
the latter. With regard to their specific star formation rates, the UCM
galaxies are intermediate objects between normal quiescent spirals and the most
extreme HII galaxies.
