Objective To establish a new technique for measurement of intrathoracic pressure in guinea-pigs. Methods When an anaesthetized guinea-pig was fixed on the back, an i.v. catheter was punctured into the thoracic cavity between the fifth and sixth costal bones. Then slowly take out its core and immediately connect its chlamyd with a pressure transducer. At this time, the computer will display the curve of intrathoracic pressure. Results i.v. catheter replacing the endothoracic catheter can be used to measure the intrathoracic pressure in guinea-pigs. Conclusion It has been shown that this method is simple and practical, hardly leading to injury to the pulmonary lobes in anlmals.