Type, severity and incidence of infection during the neutropenic period after peripheral blood stem cell transplantation (PBSCT) for treatment of malignant disease were studied in 66 patients treated at a single institution. Data of 34 female and 32 male patients with a median age of 43 years suffering from leukemia (12), lymphoma (35), multiple myeloma (six) or solid tumors (13) were retrospectively analyzed. All patients had received at least 2.5 x 10(6) CD34-positive cells for stem cell rescue after high-dose chemotherapy. Ninety-four percent of the patients experienced at least one febrile episode during their post-transplant course. The patients recovered quickly and defervesced after a median of 4 days. The incidence of bacteremia was 39% and gram-positive cocci were the predominant pathogens. In contrast, severe organ infections were rare. Only 5% of the patients suffered from lung infiltrates. No invasive fungal infections were observed. No transplant-related deaths occurred in the 66 patients studied. We conclude that the severe, but shortlasting neutropenia after peripheral blood stem cell transplantation is associated with a high incidence of bacterial infection. The severity of the majority of these infections is moderate. With appropriate anti-infective therapies these infections can be managed and life-threatening infectious complications, in particular fungal infections, are rare. Empirical anti-infective regimens specifically designed for this clinical situation should be explored.