The clinical significance of immunophenotyping of the non-Hodgkin's lymphomas is controversial. Therefore, we conducted the present study of 103 consecutively accrued diffuse large-cell lymphoma (DLCL) patients to define, independently of histologic subtypes, the prognostic importance of phenotyping. We used an extensive panel of monoclonal antibodies to T- and B-cell antigens to assign all patients immunologically into the T-cell (20 patients) or B-cell group (83 patients). The only significant differences in pretreatment clinical variables between the two patient groups were the higher frequency of bulky disease (greater than 10 cm) in B-cell patients (P = .008) and more frequent skin involvement in the T-cell group (P less than or equal to .001). Multiagent doxorubicin-containing chemotherapy regimens were employed as initial therapy in over 83% of the patients in each group. Our study revealed that disease-free survival (DFS) was significantly shorter in the T-cell patients than in the B-cell DLCL patients (median DFS, 10.8 months for T-cell and 42.7 months for B-cell; P = .01, log rank). No patient with T-cell DLCL remained disease free for longer than 2 years, whereas 55% of the B-cell group were disease free at 2 years. Univariate and multivariate analyses of all major prognostic factors of DFS suggest that the T-cell phenotype indicates an incurable subset of DLCL patients. Although the B-cell group had a twofold advantage in median survival (35 months v 18 months), actuarial overall survival was not significantly different between the two patient groups (P = .23). Our results indicate the need for new approaches in the search for a curative treatment for T-cell DLCL.