For 26 stars with effective temperatures known from directly measured angular diameters and total absolute fluxes (Code et al., 1976), HIPPARCOS parallaxes (ESA, 1997) can be used to derive empirical luminosities and radii. The empirical effective temperatures and luminosities allow a comparison of the position of these stars in the fundamental H-R diagram with evolutionary tracks. Note that no calibration, photometric or any other, is involved in the process. As noted by Jerzykiewicz & Molenda-Żakowicz (2000), the comparison shows an overall coincidence with the phases of slow nuclear burning of the solar composition evolutionary tracks, computed with OPAL opacities and moderate amount of overshooting from the convective core.
Several of the stars fall in the theoretical β Cep, SPB or δ Sct instability domains. Unfortunately, none of them is known to be an SPB variable, while the two that have been classified as δ Sct stars lack convincing evidence of variability. For the four β Cep stars that occur in the sample, the empirical radii are used to identify the radial order of pulsation.