Abstract: In order to compare the difference between the STLs measured with the ECG leadwhere the Q wave was absent and the ones measured with the lead the Q wave was present, STLs weremeasured in 47 healthy college studefits of either sex by slmultaneous recordings of carotid arterial pulsetracing, phonocardiogram and the two ECG leads, one of which was the -Q - wave-absent, and the otherwas the - Q - wave - present.The results show that the QS2 measured with the-Q - wave-absent lead and resultant PEP, PEP/LVET are all signiflcantly less than their counterparts measured with the-Q-wave-present lead (P0. 01 ). Therefore, we emphasize that the-Q - wavempresent lead should be preferentially chosen whenSTLs are measured.