Timentin (5.2 g tds) and tobramycin (40 mg tds) were administered to 51 patients (22 male, 29 female, age range 17-72, mean age 40.4) with acute leukaemia, chronic myeloid leukaemia in blastic crisis, severe aplastic anaemia and acute agranulocytopenia. All patients had neutropenia (PMN less than 1000/mm3) and fever (greater than 38 degrees C). Febrile episodes consisted of 22 proved septicaemias due to Gram-positive organisms (Staphylococcus aureus, S. epidermidis, enterococcus) in 11 cases and to Gram-negative organisms (Escherichia coli, Pseudomonas aeruginosa, Alkaligenes faecalis, Serratia marcescens, Klebsiella pneumoniae) in 10 cases. One patient had a polymicrobial infection (P. aeruginosa, S. aureus, non-haemolytic streptococcus). Twenty-nine infections were diagnosed only clinically. The mean duration of treatment was 11.1 days (range 4-20 days). Eighty-seven per cent of evaluable febrile episodes improved. Among 11 infections due to Gram-positive cocci, eight (72%) resolved, and in nine (90%) of ten cases due to Gram-negative bacilli success was obtained. The polymicrobial infection also resolved. In only four patients were mild side effects seen, e.g. exanthema, pruritus, phlebitis: renal toxicity was not observed. These data suggest that the combination of Timentin and tobramycin is an effective and safe empirical antibiotic regimen in febrile neutropenic patients.