Vancomycin (V) is widely used in neutropenic patients, though its kinetics are known in this type of patient. In the present study, ten patients were included: all of them received an intensive therapy for non-Hodgkin malignant lymphoma, Hodgkin disease, myeloma, acute leukemia, followed by an autologous bone marrow transplantation in 6 cases. All patients were neutropenic (100/mm3). The pharmacokinetic study was done at the first V administration: 1000 mg V were injected as a 1-h infusion. Plasma V concentrations were measured by an enzyme immunoassay (EMIT, Syva, France). V maximal and minimal concentrations were 61.3 +/- 38.6 micrograms/ml and 1.69 +/- 0.77 microgram/ml, respectively. Total V clearance was 158 +/- 51 ml/min, with a creatinine clearance of 141.2 +/- 36.2 ml/min on test day. V plasma kinetics can be described by a biexponential model, with the following parameters: [table: see text] These data show a 3-fold increase of initial volume of distribution and a shortened (3-fold) T1/2 beta, if compared to values obtained in normal subjects. Because the bactericidal effect is time dependent, there can be a risk of insufficient antibiotic effect throughout the day. Our data suggest that new therapeutic regimens are needed for these patients.