Human leukocyte antigen-G (HLA-G) plays a major role in escape of trophoblast cells from maternal cytotoxicity. Unless its malignant transformation, Jeg-3 choriocarcinoma cell line maintained the capacity of HLA-G production. For the analysis of function and mechanisms of HLA-G-induced immune regulation, a human cellular model with suppressed HLA-G would be very helpful. RNA interference (RNAi) is a very elegant method for this approach, but the design of appropriate oligonucleotide sequences may provide difficulties. We designed oligonucleotides to interfere exclusively with HLA-G mRNA, which were applied at different concentrations to 50% confluent Jeg-3 cells. After 36 hr, the HLA-G content in Jeg-3 cells was analyzed by Western blots. Applying the described RNAi method and oligonucleotides the cellular content of HLA-G was dose-dependently reduced as assessed in several independent Western blots. This method provides a tool for extensive investigation of HLA-G functions in vitro and in vivo.