The absolute magnitudes of δ Scuti stars derived from parallaxes measured by the Hipparcos satellite were compared with the previous estimates based on photometric uvby² indices, and significant differences were found which are related to photometric effects of metallicity and rotational velocity. A reliable calibration of Mv in terms of the photometric indices shall include an estimate of these effects. It is important also to take into account the possible presence of unresolved close companions in order to fully exploit the accuracy of Mv of nearby stars derived from the trigonometric parallaxes.

The Mv of few bright SX Phe stars support the period-luminosity relation obtained with ground based observations of globular clusters, while it does not seem to confirm the empirical dependence of this relation on the metallicity.

Some high amplitude δ Scuti stars with intermediate or normal metallicity and small and uncertain parallax have apparently a very low luminosity. Simulations of Mv determinations from observed parallaxes based on the discussion of observational errors by Lutz and Kelker (1973) have shown that the low luminosity could be an effect related to these errors.