Intratumor injections of an immune modulator, OK-432, were administered to a 61-year-old man with inoperable lung adenocarcinoma. He received intratumor injections of OK-432, 20 K.E., twice weekly, under chest ultrasound guidance. A total dose of 240 K.E. was given in a six-week period. The tumor size decreased during a six-month follow-up period after the OK-432 injections. The immunologic profile of the patient showed neutrophilia, a decrease in the lymphocyte count in the peripheral blood and an increase in immunoglobulins after the OK-432 injections. The peripheral T-lymphocyte subsets showed a significant reduction in cytotoxic T cells and a decrease in the OKT4/OKT8 ratio. Histologic examination of the tumor after OK-432 injections showed extensive desmoplastic fibrosis. There was no evidence of lymphocyte infiltration. Intratumor injections of OK-432 may be an alternative for local control of inoperable lung cancer.