The authors studied 302 hospitalized patients, 164 males and 138 females aged 15-88 years (average 66 years), with severe infections. Cefotetan was administered to 278 of them at the dose of 1 or 2 g, b.i.d. or a single daily dose i.m. Other patients [24] were treated with a continuous intravenous infusion of cefotetan (3 g daily in 5% dextrose). Of these patients 121 were treated for urinary tract infections (UTI); 114 for respiratory tract infections (RTI); 41 for liver biliary duct infections (BDI); 17 for skin or skin structure infections (SKI); 6 for fever of unknown origin and 3 for sepsis. The following Gram-positive organisms [156] were isolated: Streptococcus pneumoniae, Staphylococcus aureus and Streptococcus group D; and the following Gram-negative organisms [122]: Escherichia coli, Proteus vulgaris, Proteus mirabilis, Serratia spp., Klebsiella spp., Haemophilus influenzae and Pseudomonas aeruginosa. The overall eradication rate for Gram-positive organisms was 74% and for Gram-negative organisms it was 88%. The clinical response was satisfactory in 87.7% of patients (specifically, cefotetan was effective in 90% of UTI, 84.2% of RTI, 97.5% of BDI and 82.3% of SKI). The drug was well tolerated and side-effects (such as skin rash, diarrhoea, purpura and pain at the site of injection) occurred in only 4% of patients treated with cefotetan. In conclusion, cefotetan appears to be safe and highly effective for the treatment of severe infections in hospitalized patients.