In this work; the Doppler signals obtained from the cases of the healthy and pathologic aortic valve have been studied for determining the chaotic behaviour of the aortic valve blood flow. The Doppler signals gathered from the subject groups of healthy, stenosis and insufficiency have been evaluated by using the largest Lyapunov exponent (LLE) calculation. The LLE is accepted as an indicator of the chaos. LLE is a measure of the sensitive dependence to the initial conditions of a dynamical system and its value is positive for chaotic systems. The student-t test has been applied to the results obtained from LLE calculation of subject groups. The LLE values are positive for all groups. The LLE values of the subjects suffered from aortic insufficiency and stenosis have been found higher than those found in healthy group, significantly. The results show that the chaotic behaviour of aortic valve blood flow in stenosis and insufficiency cases is higher than healthy case.