OBJECTIVE To determine the effect of positive end-expiratory pressure (PEEP) on the respiratory system and on cardiac function. METHODS Prospective randomized study. METHODS Operating room. METHODS 60 ASA physical status 1 women scheduled for pelvic laparoscopic surgery. METHODS Patients were ventilated normally during surgery; PEEP was modified depending on patient group allocation. Group A was the control group and did not receive PEEP. Group B received PEEP 5 cmH2O and Group C received PEEP 10 cmH2O. METHODS Respiratory parameters measured were partial pressure of arterial oxygen (PaO2), partial pressure of carbon dioxide (PaCO2), and end-tidal carbon dioxide tension (ETCO2). Cardiac parameters measured were left ventricular end-diastolic volume index (LVEDVI), ie, ratio of LVEDV/body surface area (BSA; [LVEDVI = end-diastolic volume [EDV]/BSA); left ventricular (LV) systolic function, tricuspid annular plane systolic excursion (TAPSE), right ventricular (RV) fractional area change (FAC), RV dimensions in the apical 4-chamber view, tracing basal and mid-cavity minor dimensions and longitudinal dimension, cardiac index, systolic pulmonary artery pressure (PASP), and systolic RV pressure (RVSP). Respiratory and cardiac measurements were recorded at T0 (baseline); T1 (after anesthesia induction, before pneumoperitoneum induction); at 10 (T2), 20 (T3), and 30 (T4) minutes after CO2 insufflation; and at the end of surgery (T5). RESULTS Ventilation with PEEP at 10 cm H2O led to significant improvement in both respiratory and cardiac parameters. A reduction in pulmonary vascular resistance and enhanced washout of expiratory CO2 occurred. Ten and, to a lesser extent, 5 cm H2O of PEEP decreased LV stroke work. CONCLUSIONS Ventilation with PEEP (up to 10 cm H2O) recruits the hypoventilated areas of the lungs and reduces cardiac afterload.