B-cell chronic lymphocytic leukemia (B-CLL) samples were screened for alterations in multiple tumor suppressor genes (p53 (17p13), p16INK4 (9p21), and disrupted in B-cell malignancy (DBM) (13q14) by using polymerase chain reaction-based assays. Eleven percent (11 of 96) of the B-CLL cases analyzed in this study and a previous study had mutations in the p53 gene. In contrast, analysis of the p16 gene showed none of 80 B-CLL cases had mutations and five cases (6%) had homozygous deletions. Deletions of 13q14 (DBM) occurred in 18% (17 of 96) of patients surveyed. Thus, 28 of 96 cases showed an alteration in one or more of the three tumor suppressor loci examined. However, cases with p53 mutations rarely showed simultaneous loss of DBM. Our results suggest that inactivation of the tumor suppressor genes p53 and DBM may be mutually exclusive, thus providing alternate pathways for tumor development in B-CLL patients.