Augmentation of tumor immunogenicity has been increasingly studied as a strategy to develop host immunity against established malignancies. Genetic modification of tumors to secrete immunoregulatory peptides such as IL-4 has been demonstrated to augment tumor immunogenicity and enhance the induction of tumor reactive lymphoid cells in animal models. To explore the ability of IL-4 to augment the immunogenicity of melanoma cells, we constructed a recombinant retrovirus vector encoding for human IL-4 and used it to transduce human melanomas. After optimizing retrovirus transduction conditions using a reporter virus, an IL-4 encoding retrovirus vector was used to transduce early and late passage melanoma cells. IL-4 production rates of up to 2000 pg/ml per 24 h per 10(6) cells were achieved, and provirus could be detected by Southern blot of the transduced cells at 0.1 copies per cell. The IL-4 produced by the melanoma cells was biologically active. Irradiated transduced melanoma cells continued to produce IL-4 for at least two weeks of observation. Thus melanoma cells can be efficiently modified to secrete biologically active IL-4, and may be suitable substrates for autologous tumor cell vaccines.