We investigated the ventilatory changes in healthy patients without cardiopulmonary pathology during elective laparoscopic cholecystectomy in the head-up position. During surgery, intraabdominal pressure was maintained at 15 mmHg by a CO2 insufflator, and minute ventilation was controlled with a constant tidal volume and fixed respiratory rate. PETCO2 was monitored continuously and recorded every minute. Basic hemodynamic and ventilatory parameters were measured before anesthesia; after induction of anesthesia; at 5 min, 10 min and 30 min after peritoneal insufflation; and 5 min and 10 min after exsufflation. Arterial blood samples were obtained 3 times to calculate D(a-A)CO2, VD/VT, and Vco2. The latent period of PETCO2 change was 2.9 min, the ascending period was 12.6 min, and the descending period was 12.2 min. During the 71.5 min of pneumoperitoneum, V(I), VE, peak and plateau Paw increased, while Cdyn decreased significantly. Peritoneal insufflation or exsufflation also resulted in a significant change of D(a-A)CO2, D(a-A)O2, and Vco2. The anesthesiologist must be aware of both hemodynamic and ventilatory changes and must be ready to respond promptly and adequately.