The combination of ticarcillin and clavulanic acid (Timentin) was used in a nonrandomized open study in 28 patients with severe nosocomial infections. The infections were polymicrobial in 19 cases. Ten patients were bacteraemic and all were severely ill, receiving mechanical ventilation and with at least one organ system failure. Seventeen patients were treated with Timentin alone, 11 with a combination of Timentin and aminoglycosides. Timentin was used empirically, before identification of the bacteria in 14 patients (group I) and after identification of all the micro-organisms in 14 patients (group II). In group I, the empirical choice of Timentin was wrong in four cases, because at least one micro-organism was resistant to this drug. In the remaining 24 evaluable patients 12 patients were definitively cured. A relapse of the infection occurred in two cases. Five patients were initially improved but a secondary failure occurred due to a residual abscess in one case and to the underlying disease in four cases. Five initial failures due to the underlying disease in three cases were noted. The antimicrobial spectrum of Timentin is valuable in the management of nosocomial and polymicrobial infection, especially intra-abdominal infections and this study confirms a good clinical efficacy. However, combination with aminoglycosides seems mandatory, at least until the identification of all the micro-organisms involved in the infection.