Introduction. The aim of our study was to determine whether a single-dose preoperative administration of antibiotics was sufficient to prevent intra and postoperative infections in the parturients without a high risk of developing an infection, in whom the delivery was completed by cesarean section, as well as to answer whether the administered dose of antibiotics satisfied the requirements of therapeutic concentrations necessary to protect against infection in the period during the surgical procedure and during the first 6 postoperative hours. Material and methods. All investigated pregnant women were planned to have elective cesarean section as a mode of delivery. They were distributed in groups depending on the type (cephalexin, gentamycin and cephazolin) of antibiotic prophylaxis administered as a single dose. In all patients the clinical postoperative course was followed for possible infection. The concentrations of antibiotics were estimated immediately and 6h following the operation. The estimation of antibiotic concentrations was done by the method of liquid chromatography (for antibiotics belonging to the group of cephalosporins), i.e. RIA method for antibiotics from the group of aminoglycosides. Results and conclusion. The total number of infections in investigated groups was 5.18%. The measured mean concentrations of administered antibiotics following the operation and 6 h later were above MIC. This is a proof that the obtained antibiotic prophylaxis by a single dose administration of anbtibiotic is sufficient to prevent the invasion of pathogenic microorganisms from the skin.