Thirty-one patients with resistant Hodgkin's disease were treated by an identical high dose chemotherapy regimen and autologous bone marrow transplantation. Twelve of these patients received recombinant human granulocyte/macrophage colony stimulating factor (rh GM-CSF) in a phase I/II study. rh GM-CSF was administered by continuous infusion into an indwelling central venous catheter for 3-21 days at doses of 100-400 micrograms/m2/day. The patients receiving rh GM-CSF did not differ significantly from those who did not receive growth factor with regard to age, previous therapy or number of bone marrow cells infused. rh GM-CSF resulted in more rapid neutrophil regeneration, the average time to achieve a neutrophil count of greater than or equal to 0.5 x 10(9)/l being 17.5 days compared to 24.9 days in the control group (p less than 0.01). Platelet recovery was very varied and not accelerated by rh GM-CSF. Patients receiving rh GM-CSF had a similar infection rate (58% vs 68% in the control group), similar number of febrile days (5.0 vs 4.7 days) and similar period of hospitalization to the control group (30.1 vs 30.2 days). Randomized controlled trials are now required to define the clinical value of rh GM-CSF in the setting of autologous bone marrow transplantation.