This report describes a method for the determination of the longitudinal moduls of elasticity of plastics by means of Savarts pendulum. The method is applicable to products for which the characteristic determined is greater than 1500 MPa and which it is possible to prepare specimens from 1 to 5 mm in thickness by cutting. The elasticity of the test piece is employed for the transmission of energy from one pendulum to another, the test piece being used as a support for both pendulums. The amplitude of the oscillations of the driving pendulum gradually decreases until it stops. The time between starting up and the first stopping of the driving pendulum is the half-oscillation period, which is a function of the longitudinal (Young's) moduls ofelasticity of the specimen in alternating flexure.