Although effective in achieving durable remission in selected tumors incurable by conventional-dose chemotherapy, high-dose regimens requiring bone marrow transplantation remain too toxic for widespread use. With the aim to improve the therapeutic index of high-dose therapy, we have developed a novel program whereby several non-cross-resistant agents (including total body irradiation at myeloablative dose) were delivered sequentially rather than concurrently. The regimen has been tested in 25 patients with Hodgkin's disease refractory to primary chemotherapy (MOPP and ABVD) or relapsed within 12 months after first complete remission. The efficacy of the sequential regimen (72% complete response rate, 49% event-free survival and freedom from progression at four years, with a median observation of 3.5 years for patients remaining alive) compares favorably with the activity so far reported for the most effective high-dose regimens. Toxicity was low; no toxic deaths occurred and only three life-threatening adverse events were documented after autografting. The excellent tolerability of the final myeloablative course most likely reflects the speed and completeness of haematologic recovery that followed the use of peripheral blood progenitors as the sole or additional source of myeloid stem cells. The reduction of haematologic toxicity was further emphasized when rhG-CSF was employed to both shorten post-chemotherapy neutropenic intervals and to collect large amounts of peripheral blood stem cells. We expect that the use of growth factors will have a major impact on the therapeutic index of high-dose regimens. This, in turn, will confirm their safety as primary treatment in selected high-risk subsets.