Early Phase II clinical studies with bropirimine (U-54461S) having interferon (IFN) inducing and direct antiproliferative activities were conducted in patients with various solid tumors or hematologic neoplasm at 34 institutions nationwide. To investigate the safety and efficacy of the treatment, bropirimine was orally administered to the patients at the dose of 1g every two hours, three times a day for three consecutive days with a four day drug-free interval. Among the 65 patients registered, 60 patients were eligible and 44 patients completed bropirimine treatment in accordance with the respective protocols. Complete response (CR) was observed in 7 cases, and partial response (PR) was observed in 4 cases, so the efficacy rate was 25.0% (7 CRs + 4 PRs/44). Classified by target tumors, the efficacy rates were 12.9% (6 CRs/14) in bladder CIS, 33.3% 1 CR/3) in superficial bladder cancer. 11.1% 1 PR/9) in renal cell carcinoma, and 42.9% (3 PRs/7) in malignant lymphoma, respectively. Adverse drug reactions frequently observed were influenza-like symptoms such as fever (60.0%) and generalized malaise (21.7%), gastrointestinal symptoms like anorexia (56.7%) and nausea/vomiting (43.3%), and adverse effects on the circulatory system such as tachycardia (15.0%) and abnormalities in ECG (11.7%). Most of these symptoms were relieved or improved. Abnormalities in laboratory tests observed frequently were adverse effects on the liver such as elevations in GPT (33.3%), in GOT (31.7%), and in LDH (18.3%) or on the blood system like a decrease in RBC (18.3%), leukopenia (26.7%), or neutropenia (25.0%). In conclusion, bropirimine treatment proved to be effective for bladder CIS in particular, suggesting that it will be promising for use in the treatment of the disease.