Background: We have established a system for recovering Sendai virus (SeV), a nonsegmented negative strand RNA virus, entirely from cDNA at an extremely high rate, and have succeeded in creating a V(−) SeV whose gene expression was greatly enhanced by the deletion of the nonessential V gene. Because of its extreme medical importance, there has been a strong need for the establishment of a better system to express the gp120 envelope glycoprotein of the human immunodeficiency virus type 1 (HIV‐1) in sufficient quantity and purity. It also remains to be established to produce gp120 in in vitro natural host cells for HIV‐1 such as human primary blood mononuclear cells, macrophages or established T cell lines. Results: Using the above system, we created recombinant Sendai viruses expressing the gp120 in CV1 cells, a monkey kidney line. The expression level from the standard V(+) version has already reached 2.2 μg per 106 infected cells, which was readily purified from the culture fluid with a recovery rate of about 60%, and has so far appeared to be functionally and serologically authentic. The inserted gp120 gene was stably maintained during numerous passages of the recombinant virus. The V(−) version‐based expression was even more robust, consistently reaching over 6.0 μg per 106 cells, a level that is one of the highest currently attainable for gp120 production in mammalian cells. Furthermore, a broad host range of SeV allowed gp120 production in all the three natural host cells for HIV‐1 described above. Conclusions: SeV‐based expression serves as a novel choice for producing large quantities of HIV‐1 gp120 and will greatly facilitate biochemical, biological and immunological studies of this important glycoprotein.