High-dose etoposide (2 g/m(2)) plus G-CSF is a very effective regimen for peripheral blood progenitor cell (PBPC) mobilization. Unfortunately, neutropenia is common. The infectious complications associated with high-dose etoposide have not been previously described. After noting a high incidence of hospitalizations for neutropenic fever, we began a vigorous prophylactic antibiotic regimen for patients receiving high-dose etoposide plus G-CSF, attempting to reduce infectious complications. Ninety-eight patients underwent etoposide mobilization between December 1997 and June 2000. Three chronological patient groups received: (1) no specific antibiotic prophylaxis (n = 44); (2) vancomycin i.v., cefepime i.v., clarithromycin p.o., and ciprofloxacin p.o. (n = 27); and (3) vancomycin i.v., clarithromycin p.o., and ciprofloxacin p.o. (n = 27). The patients not receiving antibiotic prophylaxis had a 68% incidence of hospitalization for neutropenic fever. In the patients receiving prophylaxis, the incidence was reduced to 26% and 15% respectively, for an overall incidence of 20% (P < 0.001 for comparison between prophylaxed and unprophylaxed groups). We conclude that etoposide mobilization is associated with a significant incidence of neutropenic fever, which can be substantially reduced by a vigorous antimicrobial prophylactic program.