Eighty-eight previously autografted (78 transplanted twice and 10 once) myeloma patients who had no cryopreserved stem cells available for possible future use received G-CSF for mobilization of stem cells. One-fourth of the patients had progressive disease at the time of apheresis. All patients had received 200 mg/m2 melphalan for the first transplant. The interval between the preceding transplant and the harvest was 5-68 months (median 29). A total of 0.46-9.16 (median 3.03) x 10(6) CD34+ cells/kg were collected. More than 2 x 10(6)/kg CD34+ cells were collected in 76% of the patients, and > or = 5 x 10(6)/kg in 14%. On multivariate analysis, patients with platelet counts of > or = 200 x 10(9)/l (P < 0.0001), those who had not received any myelosuppressive chemotherapy between the last transplant and the collection (P = 0.02), and those who had received interferon-alpha for < or = 6 months (P = 0.03) had better collections. Eleven of 12 patients autografted with these cells had prompt neutrophil recovery (median 10 days to 0.5 x 10(9)/l) but recovery to 50 x 10(9)/l platelets was delayed or incomplete in 11 of 12. We conclude that it is possible to harvest peripheral blood stem cells with G-CSF stimulation in patients who have been autografted previously. Limited data suggest that platelet recovery may be suboptimal when these cells are used. These findings have practical implications for patients with malignant diseases in remission after autografting who may be candidates for future salvage therapy but have no stem cells stored, and for patients with chronic myeloid leukemia who are on long-term interferon-alpha therapy to attain cytogenetic remission for eventual collection of normal stem cells.