The use of oral prophylactic antibiotics in oncology patients is still a matter of debate. A systematic review was performed to assess the evidence for the effectiveness of oral prophylactic antibiotics to decrease bacteraemia and infection-related mortality in oncology patients during neutropenic episodes. Medline, Embase and the Cochrane register of controlled trials were searched from 1966 until 2002. The main outcome was the number of patients with documented bacteraemia (Gram-negative or Gram-positive bacteraemia) and infection related mortality. Data-extraction and quality assessment were performed independently by two reviewers. A total of 22 trials met the inclusion criteria. Seventeen trials compared prophylaxis (quinolones or Trimethoprim/sulfamethoxazole (TMP/SMZ)) to no prophylaxis. The incidence of Gram-negative bacteraemia decreased significantly (pooled OR 0.39, 95% CI 0.24-0.62) without an increase in Gram-positive bacteraemia. Quinolone-based regimens showed a stronger reduction in Gram-negative bacteraemia while TMP/SMZ based regimens were more effective in Gram-positive bacteraemia. Infection related mortality due to bacterial causes decreased with the use of prophylactic antibiotics (pooled OR 0.49, 95% CI 0.27-0.88). No increase in fungaemia or fungal related mortality was seen with the use of oral prophylaxis. In conclusion, this study has shown that oral prophylactic antibiotics decreased Gram-negative bacteraemia and infection related mortality due to bacterial causes during neutropenic episodes in oncology patients.