In recent years, the most common cause of infection in neutropenic patients has shifted from Gram-negative to Gram-positive bacteria. To compare the efficacy and toxicity of teicoplanin and vancomycin in neutropenic patients, we conducted a prospective study of 151 adult leukaemic patients hospitalized for intensive chemotherapy. After chemotherapy, the median duration of granulocytopenia (less than 500/mm3) was 25 d (range 13-49). When the patients became febrile, they received ceftazidime (CTZ) alone (2 g every 12 h, intravenously). If fever persisted more than 48-72 h after administration of CTZ, the patients were randomly assigned to receive CTZ combined with either vancomycin (vanco) (30 mg/kg/d) or teicoplanin (teico) (6 mg/kg every 12 h on day 1, then daily). When fever persisted further, an aminoglycoside antibiotic and/or amphotericin B were usually added to the previous combination. Of the 151 patients, 116 patients became febrile during the period of aplasia. Fifty-nine patients had persistent (or recurrent) fever despite administration of CTZ and received either vanco (n = 35) or teico (n = 24). Sixteen of these latter 59 patients had septicaemia (vanco n = 9; teico n = 7) due to Candida sp. (n = 2), Gram-negative (n = 2) or Gram-positive (n = 12) bacteria. The main characteristics of patients and infection were similar in both arms. The treatment was considered as a success (disappearance of fever within 48 h) in 21/35 patients of the vanco group (60%) compared to 13/24 patients of the teico group (54%; P not significant). The percentage of failures for infection due to Gram-positive bacteria was 2/11 for vanco versus 2/7 for teico (P not significant). Two patients in each group died from infection. The main cause of failure was retrospectively attributed to fungal pathogens. No major toxic effects were found in either group. These preliminary results do not show any difference between vanco and teico as second-line antibiotic therapy in leukaemic patients with severe and prolonged granulocytopenia.