  With the goal of confirming the metallicity "excess" present in stars with
planetary-mass companions, we present in this paper a high-precision
spectroscopic study of a sample of dwarfs included in the CORALIE extrasolar
planet survey. The targets were chosen according to the basic criteria that 1)
they formed part of a limited volume and 2) they did not present the signature
of a planetary host companion. A few stars with planets were also observed and
analysed; namely, HD 6434, HD 13445, HD 16141, HD 17051, HD 19994, HD 22049, HD
28185, HD 38529, HD 52265, HD 190228, HD 210277 and HD 217107. For some of
these objects there had been no previous spectroscopic studies. The
spectroscopic analysis was done using the same technique as in previous work on
the metallicity of stars with planets, thereby permitting a direct comparison
of the results. The work described in this paper thus represents the first
uniform and unbiased comparison between stars with and without planetary-mass
companions in a volume-limited sample. The results show that 1) stars with
planets are significantly metal-rich, and 2) that the source of the metallicity
is most probably "primordial". The results presented here may impose serious
constraints on planetary system formation and evolution models.
