The most effective method for the delivery of cisplatin chemotherapy in the treatment of epithelial ovarian cancer limited to the presence of microscopic intraperitoneal disease is a controversial issue. The use of intravenous (iv) versus intraperitoneal (ip) cisplatin was evaluated in a murine tumor model of human epithelial ovarian cancer. Using single dose cisplatin therapy for microscopic disease limited to positive cytology of abdominal disease and microscopic peritoneal involvement, ip therapy had significantly greater (P less than 0.001) survival time than iv therapy (28 +/- 1.6 days vs. 23 +/- 1.6 days, respectively). Once ascites and macroscopically evident intraperitoneal tumor became apparent, no difference could be found in survival time based on iv versus ip therapy (16 +/- 3 days for both groups); though both forms of therapy significantly (P less than 0.05) prolonged survival in mice with macroscopic disease when compared to control animals (13 +/- 1.2 days). The evidence presented implies that ip cisplatin therapy is significantly more effective than iv therapy when dealing with microscopic intraperitoneal disease.