Previous statistical results have shown that the pairwise velocity dis
persion sigma(g)(r(p)) of galaxies at small separations (r(p) almost-e
qual-to 1 h-1 Mpc) is about 300 km s-1. This value is significantly lo
wer than the predictions of currently favoured models of structure for
mation, unless a large pairwise velocity bias exists between galaxies
and the underlying mass. Using various samples of galaxies (CfA, SSRS,
IRAS, CfA slice, samples containing ellipticals or spirals), we show
that the results of sigma(g)(r(p)) are sensitive to sampling effects,
such as the inclusion of dominating clusters, and the correction of th
e Virgocentric infall. The value of sigma(g)(r(p) = 1 h-1 Mpc) is as h
igh as approximately 1000 km s-1 for the CfA slice including Coma, and
as low as approximately 300 km s-1 for the spiral sample and for the
CfA sample with a correction of the Virgocentric infall. The values of
sigma(g) that we obtain are consistent with the high values predicted
by currently favoured models of structure formation, which suggests t
hat a high pairwise velocity bias between galaxies and mass is not req
uired by present data.