The intracavitary injection of OK-432 (a streptococcal preparation) with subcutaneous priming has been shown to be an effective immunotherapy for patients with malignant effusion. We applied this treatment in a case of advanced renal cell carcinoma with massive ascites. The patient received 0.2 Klinishe Einheit (KE) OK-432 in the subcutaneous injection twice (day 1 and day 7) followed by 10KE OK-432 intra-abdominal administration (day 9). The treatment was performed safely without major side-effects except for transient pyrexia. A significant reduction of ascites was noted 1 month after the treatment without subsequent re-accumulation. Intracavitary injection of OK-432 with subcutaneous priming seems to be a simple, safe and effective treatment for ascites in advanced renal cell carcinoma.