According to the principle of linear character of each 10% FVC segment on the FVC-t curve proposed by Jordanoglou, the slope of each segment is nearly equal to 0.1 FVC/2 MMTp. Then MTTp approximately 0.1 FVC/2Vp. The calculations of MTTp at high, middle and low lung volumes are MTT20-30% = 0.1 FVC/2V75, MTT45-55% = 0.1 FVC/2V50, and MTT70-80% = 0.1 FVC/2 V25. The MTTp of 628 cases of normal children and adolescents aged 6-19 yr. was measured by this method. In comparison with the direct method, the results showed that there was no significant difference between the 2 methods. The regression equations built with age as an independent variable showed a good correlation. Obviously, this method is easily performed, and is suitable for the wide use of MTTp.