  Star forming galaxies represent a small yet sizable fraction of the X-ray sky
(1%-20%, depending on the flux). X-ray surveys allow to derive their luminosity
function and evolution, free from uncertainties due to absorption. However,
much care must be put in the selection criteria to build samples clean from
contamination by AGN. Here we review the possibilities offered by the proposed
WFXT mission for their study. We analyze the expected luminosity and redshift
distributions of star forming galaxies in the proposed WFXT surveys. We discuss
the impact of such a mission on the knowledge of the cosmic star formation
history, and provide a few suggestions.
