In a prospective open trial, 21 female patients undergoing breast surgery received a single intravenous bolus injection of teicoplanin, 400 mg, 30 minutes before the operation. During surgery, (1 hour after teicoplanin administration), samples of breast and fat tissue and serum were collected; 24 hours and 48 hours after dosing, samples of wound exudate were taken. Teicoplanin concentrations were determined using the RASA method. Teicoplanin levels were lowest in fat tissue. Teicoplanin levels in wound exudate were found to be satisfactorily high. However, teicoplanin levels in fat and breast tissue and in wound exudate exceeded the MIC90 for various staphylococcus strains, such as S. aureus and S. epidermidis. No local or systemic adverse reactions were observed during the trial. Teicoplanin was well tolerated. Preliminary results from this trial, therefore, indicate that teicoplanin may be a suitable antibiotic for use in the prophylaxis of infection in breast surgery.