A couple of sbuttle vectors (pYNA and pYNB), containing a sequence coding for the leader regionof the α-factor precursor (α-factor leader sequence) and the origin of 2μm circle, were constructed. ThecDNA for the β-hCG (145aa) was fused in phase to the 3’-end of the α-factor leader sequence andtransformed into the yeast Saccharomyces cercvisiae. The yeast cells carrying this hybrid gene synthesizedand secreted a protein with the immunoactivity of β-hCG in an amount of 45μg per liter of culture. Thepreliminary characterization of this protein is also reported in this paper. The cDNA for the β-hCG (145 aa) was amplified by PCR from a vector (pYNA and pYNB) containing a sequence coding for the leader region of the α-factor precursor (α-factor leader sequence) and the origin of 2 μm circle, was fused in phase to the 3’-end of the α-factor leader sequence and transformed into the yeast Saccharomyces cercvisiae. The yeast cells carried this hybrid gene synthesized and secreted a protein with the immunoactivity of β-hCG in an amount of 45 μg per liter of culture. The preliminary characterization of this protein is also reported in this paper.