The star formation rate (SFR) was determined from a sample of 36 late-type galaxies (14 dS and 22 Sm), from the SFR(H α ) and far ultraviolet (FUV) flux. We found that the SFR(FUV) is higher in most cases, larger for Sm galaxies and smaller for barred galaxies, for any morphological type, in both diagnostic methods. In addition, a study of the spatial distribution of star formation within these galaxies was made. We concluded that there is no preferential place for the star formation. Finally, we studied the role of the diffuse ionized gas in the SFR value; we found that the H α flux contribution from this gas should not be included in the SFR determination unless it is verified that leaking photons are the only source of the neutral gas ionization.

Due to a mistake, Figs. 1a, 1b, 1c and 2b are incorrect. Those spectra have been replaced and appear in the electronic version of the article.Send offprint requests to: K. Olofsson,