The clinical significance of immunophenotyping of the non-Hodgkin's lymphomas (NHL) is still controversial. Therefore, we evaluated the prognostic significance of T- and B-cell phenotype in 102 patients having diffuse non-Hodgkin's lymphoma who had been treated in a majority with Adriamycin-containing regimens. The significant differences in pretreatment clinical variables between the two patient groups were the higher frequency of markedly elevated LDH (greater than or equal to X 2 normal) and the lower frequency of decreased cholesterol level in B-NHL (p less than 0.05). Patients with B-NHL had a higher complete remission (CR) rate (77% vs 59%: p = NS), a significantly better overall survival (62% vs 34% at 3-years: p less than 0.05) and longer duration of remission for all patients (50% vs 27% at 3-years: p less than 0.05). Among forty-five patients with stages III and IV disease of nodal origin (excluding those with diffuse small cleaved histology), the B-cell group was associated with a better prognosis; a higher CR rate (68% vs 41%: p = NS) and a longer duration of remission for all patients (44% vs 12% at 2-years: p less than 0.05). Furthermore, for patients with T-cell phenotype, the primary site was the only prognostic factor; the patients whose disease originated from Waldeyer's ring, nasal cavity, and paranasal sinuses, achieved a better CR rate (92% vs 40%: p less than 0.05) and a longer duration of remission for all patients (48% vs 15% at 2-years: p less than 0.05). We conclude that advanced T-cell lymphoma of nodal origin is a subgroup of patients with very poor prognosis if treated with less intensive chemotherapeutic regimens.