Patients with disseminated follicular non-Hodgkin's lymphoma (NHL) are only occasionally cured with standard chemotherapy regimens. Although most of these tumors are initially responsive to chemotherapy, in 40% to 70% of patients the lymphoma will eventually transform to an NHL of higher grade malignancy and a poorer prognosis. We treated 18 patients having an original diagnosis of follicular NHL with high-dose therapy and autologous bone marrow transplantation. The lymphomas of 10 of the patients had already undergone histologic transformation and eight still had a follicular histologic pattern. The former group had been followed for a longer time from the diagnosis of NHL and had been more extensively treated with conventional chemotherapy regimens. All eight patients with follicular NHL at the time of transplantation are alive for 246+ to 1,804+ days and seven of the patients are in complete remission. In contrast, of the 10 patients in histologic transformation only 1 is alive and in CR. This reflects the inability of these patients to tolerate the high-dose chemotherapy and myelosuppression as well as resistance of their lymphoma to this therapy. This difference in survival between the two groups was highly significant (P = .002). We conclude that the outcome of patients with follicular NHL transplanted early before histologic transformation is better than for those who are transplanted later in the course of their illness. Because of the relapsing behavior of follicular NHL, a longer follow-up is necessary to prove any impact on the natural history of the disease.