Twenty-nine patients with non-Hodgkin's lymphoma received a single subcutaneous injection of 6 mg pegfilgrastim approximately 24 h after the start of CHOP chemotherapy. The safety of pegfilgrastim in this patient population was determined by reports of adverse events. The pharmacokinetics of pegfilgrastim were characterized and the duration of grade 4 neutropenia, time to absolute neutrophil count (ANC) recovery to > or = 2.0 x 10(9)/l, neutrophil nadir, and incidence of febrile neutropenia were determined in the first 21-day chemotherapy cycle. The incidence of grade 4 neutropenia in cycle 1 was 43% with a mean (SD) duration of grade 4 neutropenia value of 1.0 (1.4) day. No apparent relationship between the duration of grade 4 neutropenia and body weight was observed. The median [quartiles] time to ANC recovery was 10 [9, 11] days. The incidence of febrile neutropenia was 11%. No unexpected adverse events were reported and no patient developed antibodies to pegfilgrastim. Serum concentration of pegfilgrastim reached a maximum (median [quartiles]) of 128 [58, 159] ng/ml at approximately 24 h after administration, and was followed by a second smaller peak (median [quartiles]) of 10.6 [3.0, 20.5] ng/ml at the time of the neutrophil nadir. After the second peak, concentration of pegfilgrastim declined linearly with a median terminal half-life of approximately 42 h.