Neutropenic episodes in kidney transplant patients are poorly characterized. In this retrospective study, neutropenia was experienced by 112/395 patients (28%) during the first year posttransplant. The only factor found to be significantly associated with the occurrence of neutropenia was combined tacrolimus-mycophenolate therapy (p < 0.001). Neutropenic patients experienced more bacterial infections (43% vs. 32%, p = 0.04). Grade of neutropenia correlated with the global risk of infection. Discontinuation of mycophenolic acid (MPA) due to neutropenia was associated with an increased incidence of acute rejection (odds ratios per day 1.11, 95% confidence intervals 1.02-1.22) but not with reduced renal function at 1 year. The time from onset of neutropenia to MPA discontinuation correlated with the duration of neutropenia. Granulocyte colony-stimulating factor (G-CSF) administration was safe and effective in severely neutropenic kidney graft recipients, with absolute neutrophil count >1000/microL achieved in a mean of 1.5+/-0.5 days. Neutropenia is an important and frequent laboratory finding that may exert a significant influence on outcomes in kidney transplantation. As well as leading to an increased incidence of infection, it is associated with a higher rate of allograft rejection if MPA is discontinued for >6 days (p = 0.02). G-CSF accelerates recovery of neutropenia and may be a good therapeutic alternative for severely neutropenic patients.