To explore a new approach to express HIV-2 external glycoprotein gp105 in methyltrophic yeast, Pichia pastoris, the gp 105 gene was obtained by PCR amplification and was cloned into the secreted expression vector pHILS1. The positive recombinant Pichia pastoris strains were screened and identified by PCR after electroporation and induction by methanol of the gp105 expression. SDS-PAGE and Western blot analyses showed that gp105, unlike gp120 from HIV-1, could be secreted into medium by recombinant Pichia pastoris strain, and the expressed product of a 90 kD glycoprotein showed satisfactory antigenicity with specific antibody.