During an 8-month period, Klebsiella pneumoniae resistant to cefotaxime and ceftazidime were isolated from 18 elderly patients in two closely-situated UK hospitals. Amongst these 18 patients, the organisms were isolated from urine samples of 17, from blood cultures of two and from a wound swab of one. The infected patients were located in nine different wards and several of the patients had been transferred between wards, within and between the two hospitals. All the bacterial isolates belonged to serotype K62, were non-typable or reacted only weakly with bacteriophage, showed similar plasmid profiles and were resistant to tetracycline and trimethoprim, thus indicating they were the same strain. Resistance to cefotaxime and ceftazidime was inhibited by clavulanic acid suggesting the involvement of extended-spectrum beta-lactamase (ESBL) enzyme activity. This was confirmed by analytical isoelectric focusing, which showed that isolates each produced two beta-lactamases with isoelectric points of 7.0(SHV-3) and 7.6 (SHV-1/2) respectively.