So far, reproducible histomorphologic and immunological criteria to distinguish clinicopathologic subtypes of blastic peripheral B-cell non-Hodgkin's lymphoma (BBCL), especially centroblastic (cb) and immunoblastic (ib) lymphomas, for daily diagnostic use are still lacking. Therefore, we correlated the cytogenetic findings in 126 patients with BBCL with histopathologic diagnoses. Subclassification of cb and ib lymphomas relied on the criteria defined in the updated Kiel classification; these subtypes are also listed in the Revised European-American Lymphoma (REAL) classification and in a preliminary report on the newly established World Health Organization classification, to investigate their clinical significance. Moreover, we performed a multivariate analysis to compare the prognostic significance of cytogenetic findings with the International Index. There were significant differences in the frequency of chromosome aberrations between different BBCL subtypes: t(8;14) was predominantly present in Burkitt's lymphomas, t(14;18) in centroblastic lymphomas, deletions in 8q and 14q, changes of 4q and losses of chromosome 10 in immunoblastic lymphomas; t(11;14) was restricted to blastoid mantle cell lymphomas and associated with a poor prognosis. In cb lymphomas, deletions in 1q42-qter, duplications in 1q23-32, trisomy 5, and changes of 15q were identified as independent prognostic factors. In ib lymphomas, changes of 7q and 8q had stronger impact on survival than the International Index. These findings underline that Burkitt's, cb, ib, and blastoid mantle-cell lymphoma are biologically distinct and clinically relevant entities and that cytogenetic findings can be helpful to subtype BBCL.