Although superficial bladder cancer, usually presenting as low grade transitional cell carcinomas, are easily resected by transurethral intervention, their frequent recurrence and progression of satage or grade of the recurrent tumors in some cases is a major problem in urology. Deletion of chromosome 9, bands 9p21-22 in bladder cancers including the lowest grade and stage, suggest potential location of candidate tumor suppressor genes. Recently, p16/MTS1 was isolated from 9p21-22 as a multiple tumor suppressor gene, which regulates the cyclin dependent kinase 4 in the G1/S phase of the cell cycle. In the present study, somatic alterations of p16/MTS1 were examined concentrating on histologically defined superficial bladder carcinomas by polymerase chain reaction (PCR)-single strand conformation polymorphism (SSCP) technique using paraffin embedded materials. Infrequent alterations of p16/MTS1 in superficial bladder cancers, one deletion and one silent mutation in 15 cases, were detected. The results suggest that p16/MTS1 mutation is not involved in the development of superficial urinary bladder carcinomas.