Following induction therapy and 4 g/m(2) cyclophosphamide, a single dose of 12 mg polyethyleneglycol-conjugated G-CSF (pegfilgrastim; n=12) or daily doses of unconjugated G-CSF (8.5 mug/kg/day) (n=12) were administered to myeloma patients. Pegfilgrastim was associated with an earlier leukocyte recovery (12 vs 14 days) and peripheral blood CD34+ cell peak (12 vs 15 days). The peripheral blood CD34+ cell peak was lower in the pegfilgrastim group (78 vs 111/mul). Following high-dose melphalan (200 mg/m(2)) and autografting, leukocyte and platelet reconstitution was similar in both groups and stable blood counts were observed 100 days post transplant. In summary, a single dose of pegfilgrastim after chemotherapy is capable of mobilizing a sufficient number of CD34+ cells for successful autografting with early engraftment and sustained hematological reconstitution in patients with myeloma. These data provide the basis for randomized studies evaluating the optimal dose and time of pegfilgrastim as well as long-term outcome in larger cohorts of patients.