Neutropenia in solid organ transplant recipients may be caused by immunosuppressive therapy, antimicrobial therapy, as well as bacterial and viral infections. Filgrastim, a human granulocyte colony stimulating factor (G-CSF) is used for the reversal of neutropenia. Although its influence is principally restricted to neutrophil progenitors, the safety of G-CSF in terms of percipitating or aggravating allograft rejection and its efficacy in reversing neutropenia in kidney and combined kidney and pancreas transplant patients has not been studied or reported. In this study we retrospectively analyzed the use of G-CSF between March 1992 and May 1994 at the University of Cincinnati Medical Center, in patients who received either a kidney or a combined kidney and pancreas transplant. A total of 25 patients developed 35 episodes of neutropenia and received an average of 2.9 doses of G-CSF per episode. The mean WBC nadir was 2.6 x 10(3)/cu mm with an average peak WBC count of 15.5 x 10(3)/cu mm following treatment (p = < 0.00001). The average number of days to peak WBC after initiation of treatment was 4.6 days. The mean pre-treatment serum creatinine level was 2.3 mg/dl and the peak serum creatinine in the week following treatment remained the same. We conclude that G-CSF is an effective treatment in reversing neutropenia in renal transplant recipients and does not precipitate or aggravate allograft rejection.