Purpose: To evaluate the safety of repifermin (keratinocyte growth factor-2) administered before and after aetologous hematopoietic stem cell transplantation (auto-HSCT). A preliminary analysis of the ability of keratinocyte growth factor-2 to prevent mucositis was also done. Experimental Design: Forty-two patients received intravenous repifermin (25 μg/kg or 50 μg/kg) or placebo for 3 days before their auto-HSCT conditioning regimen and for up to 10 days after auto-HSCT. Within each dose level, 14 patients were randomized to repifermin and 7 patients to placebo. Clinical evaluations of mucositis were scheduled before auto-HSCT conditioning regimen, on the day of transplant, and three times per week until mucositis resolved. Results: In general, the incidence of adverse events was similar for patients treated with repifermin and placebo. No clinically meaningful differences were noted among treatment groups for clinical laboratory variables. Treatment groups experienced similar time to engraftment. The frequency of Grade 2 to 4 mucositis was 100% for patients in the placebo group, 64% for patients in the 25 μg/kg group (P = 0.041 versus placebo), and 50% for patients in the 50 μg/kg group (P = 0.006 versus placebo). Results of other endpoints, including pain on swallowing and use of pain medication specifically for mucositis, suggested a better outcome for patients in the 50 μg/kg group compared with the placebo and 25 μg/kg groups. Conclusions: Repifermin was well tolerated. Repifermin given before and after auto-HSCT seems to be active in reducing mocositis, but a larger trial will be necessary to determine the efficacy of repifermin with this dose schedule.