Several δ Scuti stars (A/F stars) have been observed during multi-site campaigns of observations and have been found to be multiperiodic pulsators. They are thus good candidates for asteroseismology from ground based observations. Observations provide the position of the star in the H-R diagram and some frequencies (about 5 for the STEPHI campaigns). Comparisons with models should then allow to identify the oscillation modes of the star and then give information on the unknown parameters of the star (mass, age, chemical composition). However the situation is complicated, since stellar models are based on a physical description of the stellar material, which is not well known in many respects. In particular A/F stars have convective cores, the extent of which depends on the amount of overshooting considered and on the description of this process.