38 patients with severe acute bacterial systemic infections have been enrolled in this study: 19 patients were treated with piperacillin (100-200 mg/kg/day) and 19 with ceftazidime (45-90 mg/kg/day) by i.v. route. In both groups monotherapy has been found effective and well tolerated. Serious side-effects have not been observed. The high cure and eradication rates in both groups do not show statistically significant differences (chi 2 = 0.620 and chi 2 = 0.219, respectively, p greater than 0.05).