Erythromycin is well-known for its properties of tissular diffusion. An estimation of its concentration in uterine tissue seemed worthwhile, in order to justify the use of erythromycin lactobionate in uterine infections by sensitive micro-organisms. The authors studied the uterine levels of this macrolid, after perfusion of 1g of erythromycin lactobionate, over a period of one hour. The protocol involved a group of 15 women, who were to undergo a hysterectomy for benign non-inflammatory pathology. The uterine specimens and plasmatic pharmacokinetics of the antibiotic constitute the data. The concentrations of antibiotic were determined by microbiological methods. 2 sets of results emerge: during perfusion, the uterine erythromycin levels are equal or inferior to simultaneous serum levels. after perfusion, the uterine levels are superior to serum levels. A bicompartmental linear model was used, which simulated the tissular levels in standard treatment with erythromycin lactobionate. If the erythromycin 4 micrograms/ml critical concentration is compared with uterine tissue concentration, the antibiotic may be expected to be active against a uterine affected by sensitive micro-organisms during a period of approximately 5 hours. This result must be confirmed by a clinical study.