Infectious complications are frequent events in patients undergoing high-dose cytotoxic chemotherapy with subsequent autologous peripheral blood stem cell transplantation (PBSCT). To evaluate whether a single subcutaneous injection of pegfilgrastim (6 mg) is as safe and effective as daily filgrastim (5 mug/kg/day), 60 consecutive autologous stem cell transplantations performed for various haematological malignancies have been analysed. In total, 24 patients undergoing 30 consecutive PBSCT received a single subcutaneous injection of 6 mg pegfilgrastim on day 5 after transplantation and were compared retrospectively with 30 patients receiving 5 mug/kg/day of filgrastim starting from day 7 post transplantation. The mean duration of grade 4 neutropenia in the pegfilgrastim and filgrastim groups was 8.3 and 9.5 days, respectively (P=0.047). The results of the two groups were not significantly different for incidence of febrile neutropenia and toxicity profile. However, duration of febrile neutropenia (1.6 vs 3.0 days) and total days of fever (1.73 vs 4.1) were different (P=0.017 and 0.003, respectively), favouring the pegfilgrastim arm. Consequently, a higher incidence of transplants with documented infectious complications associated with the filgrastim group could be observed (56 vs 26%) (P=0.02). A single injection of pegfilgrastim administered at day 5 post transplant shows comparable safety and efficacy profiles to daily injections of filgrastim.