Examination of IRAS results for a sample of nearby galaxies with RC2 types between SO/a and Scd (inclusive) suggests that the only galaxies in which the IRAS colours are dominated by emission from warm dust in star formation regions are barred (Hawarden et al. 1985). Figure 1 is a 2-colour diagram of all Shapley-Ames spiral galaxies of the above types detected by IRAS in all four wavebands. It shows the ratio of fluxes in the IRAS 25 and 12 micron bands as a function of the ratio of fluxes in the 100 and 25 micron bands. On this diagram the SA systems, with the exception of a few Seyferts, have small 25/12 ratios and large 100/25 ratios. In sharp contrast, a large fraction of the SB galaxies and many SAB galaxies (not shown) have greatly enhanced 25 micron fluxes indicative of large amounts of dust at temperatures such as are commonly observed in regions of current star formation.