BACKGROUND: To evaluate the effects of pneumoperitoneum and posture on total respiratory compliance, peak inspiratory airway pressure and inspiratory minute ventilation during laparoscopic pneumoperitoneum and pelviscopic surgery we monitored continuously with continuous spirometry. METHODS: 20 patients were anesthetized and paralyzed, tracheally intubated and mechanically ventilated at te rate of 12/min and at a tidal volume of 10 ml/kg. Measurements were made before surgery, just before insufflation and 5, 10, 20, 30, 60 min after insufflation under position changed (10o reverse Trendelenburg position in laparoscopic cholecystectomy; group C, 10o Trendelenburg and lithotomy position in pelviscopic surgery; group P), and 5, 10 min after deflation under horizontal position. Compliance, peak inspiratory airway pressure and inspiratory minute volume were monitored continuously with side stream spirometry. RESULTS: Compliance of respiratory system decreased 39.8% and 39.1%, peak inspiratory pressure increased 43.5% and 61.3%, inspiratory minute volume decreased 10.9% and 9.1% under pneumoperitoneum in group C and group P. CONCLUSION: Increased intrabdominal pressure and posture during laparoscopic cholecystectomy and pelviscopic surgery cause significant decreased respiratory compliance and inspiratory minute volume and a significant increased airway pressure. On-line monitoring of respiratory volume, pressure and compliance may be helpful during general anesthesia to avoid the potential harmful effects of increased airway pressure occurring with increased intra-abdominal pressure.