The effectiveness of temocillin in the treatment of culture-proven Gram-negative septicaemia was investigated in 22 adult patients, most of whom were elderly with serious underlying diseases. Administration of temocillin 2g twice daily to 15 patients or 1g twice daily to 7 patients resulted in clinical cure in 15 patients (68%), while 4 responded partially (18%) and 3 were considered failures (14%). The original pathogen was eradicated from 20 of 21 assessable patients (95%), 1 patient was unassessable and 1 was considered a failure. Superinfection was documented in 4 patients, originating twice in a central venous catheter, once in the urinary tract and once in an unidentified source. No clinical nor biological side effects were observed except for pain at the injection site in 1 patient who received the drug intramuscularly. We conclude that temocillin in monotherapy can be used effectively for proven Gram-negative septicaemia, and that the safety of the drug makes it particularly valuable in the elderly.