Chimeric simian and human immunodeficiency viruses (SHIVs) are useful tool for investigating AIDS pathogenesis and for development of vaccine. We constructed a SHIV-vpr vector (designated as SHIV-3sj) by replacing vpr region with restriction enzyme sites. SHIV-3sj was designed to express inserted gene along with its viral replication. Five cytokine genes were inserted into SHIV-3sj, and ability of viral replication and expression of the inserted genes were examined. The short insert including RANTES and IL-5 resulted in the successful expression from SHIV-3sj, while the construct having longer genes including IL-2, IL-6 and IL-12p35 failed to become replication competent. These results suggest that the length of the insert is an important factor for the replication ability of SHIV-3sj vector.