Liolaemus goetschi, L. darwini and L. boulengeri may be assembled in a natural species group. They are characterized by a number of common morphological features, but their specific differentiation appears more evident in males. Females of L. goetschi and L. boulengeri are very similar, quite indistinguishable. Serological researches support a very near relationship between L. goetschi and L. boulengeri, in accordance with their morphological affinities. The serological distance increases between L. darwini and L. goetschi and it is stronger between L. darwini and L. boulengeri.