Ceftazidime was administered to 41 patients with serious infections caused by Pseudomonas aeruginosa (24 cases) and other bacteria (17 cases). The clinical response rate of pseudomonas infections (88%) was similar to that of other bacteria (94%) with microbiological eradication of 83% of initial pseudomonas isolates compared to 82% of non-pseudomonas strains. The development of resistance to ceftazidime during therapy was observed in 3 cases (Enterobacter agglomerans, Enterobacter cloacae, and Ps. aeruginosa), and superinfection by a resistant Enterobacter agglomerans occurred in one case. Adverse reactions of clinical significance included two cases of leukopenia and one case each of azotaemia, diarrhoea (Clostridium difficile toxin positive), and rash.