  We show that there is a relationship between the age excess, defined as the
difference between the stellar isochrone and chromospheric ages, and the
metallicity as measured by the index [Fe/H] for late-type dwarfs. The
chromospheric age tends to be lower than the isochrone age for metal-poor
stars, and the opposite occurs for metal-rich objects. We suggest that this
could be an effect of neglecting the metallicity dependence of the calibrated
chromospheric emission-age relation. We propose a correction to account for
this dependence. We also investigate the metallicity distributions of these
stars, and show that there are distinct trends according to the chromospheric
activity level. Inactive stars have a metallicity distribution which resembles
the metallicity distribution of solar neighbourhood stars (Rocha-Pinto & Maciel
1996), while active stars appear to be concentrated in an activity strip on the
log R'HK - [Fe/H] diagram. We provide some explanations for these trends, and
show that the chromospheric emission-age relation probably has different slopes
on the two sides of the Vaughan-Preston gap.
