In an open, non-comparative study 40 patients with severe, often life-threatening infections, were treated with Timentin 5.2 g (5 g ticarcillin plus 200 mg potassium clavulanate) by iv infusion every 6 or 8 h. They were suffering from septicaemia (9), obstructed UTI (8), non-obstructed urinary tract infection (10), respiratory tract infection (6), infected burns (4) or malignant otitis externa (3). Many patients had important aggravating factors such as renal transplantation, peritoneal or haemodialysis, leukaemia, extensive burns, renal stones, tracheostomy and diabetes. Pathogens included Pseudomonas aeruginosa (21), Escherichia coli (7), and other Enterobacteriaceae (6). Twenty-four pathogens (13 P. aeruginosa) were ticarcillin-resistant. Thirty-six patients were clinically cured including all cases of malignant otitis externa, infected burns and non-obstructed urinary tract infection. Three patients improved and one patient with obstructed urinary tract infection failed. In 32 patients the pathogen was eradicated, in one patient it persisted and in seven it reappeared. In particular, 11 of 13 patients with infections due to ticarcillin-resistant P. aeruginosa were cured and two improved. There was, however, bacteriological relapse in five. There were no side-effects or evidence of toxicity in any of the patients. In an in-vitro study a synergistic effect between ticarcillin and clavulanate was noted against Enterobacteriaceae but only a slight synergistic effect against P. aeruginosa. Studies in patients with normal liver and kidney function showed pharmacokinetic compatibility of the two agents. Timentin can be recommended for the initial treatment of serious infections.