Meropenem is a new broad spectrum carbapenem antibiotic which can be administered as monotherapy for serious infections. The efficacy and safety of meropenem was compared with that of ceftazidime (alone or in combination with amikacin) in 153 patients with septicaemia who were enrolled into identical, prospective, randomised studies. Forty-five patients with infections arising from the urinary or lower respiratory tracts were given either meropenem 500 mg or ceftazidime 250-1000 mg intravenously every 8 h; 108 patients with more serious infections were given meropenem 1 g or ceftazidime 2 g every 8 h +/- amikacin 15 mg/kg/day. Overall, 71 patients received meropenem, 47 ceftazidime and 35 ceftazidime plus amikacin. Comparable clinical response rates were achieved in the meropenem and ceftazidime/amikacin groups (92% vs 94% at the end of therapy respectively). Furthermore, a satisfactory bacteriological response was obtained in all evaluable patients. The most common pathogens isolated were Escherichia coli, Streptococcus pneumoniae and Pseudomonas aeruginosa. Relapse occurred in one patient in the ceftazidime/amikacin group, who had a mixed infection of E. coli and P. aeruginosa. There were no relapses in the meropenem group. Both treatments were well tolerated and only one patient had to withdraw from the trial because of an adverse effect (rash associated with ceftazidime). In conclusion, these data confirm that meropenem monotherapy is well tolerated and is as effective as ceftazidime (alone or combined with amikacin) in the empirical treatment of septicaemia. It should prove to be a useful addition to the drugs currently available for this life-threatening disease.