An experimental model in Wistar rats, of osteomyelitis caused by Escherichia coli, was used to evaluate the efficacy of cefotaxime in two treatment regimens of different durations. Four groups of rats were set up: a group of rats receiving short-term treatment (14 days) with subcutaneous cefotaxime (100 mg bd), killed after 56 days; a control group receiving no treatment, killed after 56 days; a group of rats undergoing long-term treatment (28 days) with subcutaneous cefotaxime as above, killed after 70 days and a control group of rats receiving no treatment, killed after 70 days. Analysis of histopathological and microbiological findings revealed significantly better results in the long-term treatment group. No side-effects were observed during treatment or afterwards.