Wave nature of heat propagation in a very thin _lm subjected to an exponentially decaying temperature change on both sides is investigated by solving the hyperbolic heat conduction equation[ Analytical expressions are obtained for the temperature and heat ~ux distributions[ Numerical computations are performed in order to determine the behavior of temperature and heat ~ux distributions before and after the collision of the wave fronts from two sides of the _lm[ It is disclosed that in transient heat conduction a heat pulse is transported as a wave only when the decaying frequency of wall temperature equals the reciprocal of thermal relaxation time of the medium "v 0:t#\ which is attenuated in the _lm\ and that non!Fourier heat conduction is extremely signi_cant with certain range of _lm thickness and time[ The Fourier|s law used in macroscale heat conduction cannot be applied[ The results also show that both temperature overshoot and temperature undershoot occur in the _lms with smaller values of x 9 :tC within a very short period of time\ and that the _rst reverse ~ow of heat occurs at the same moment b 9[68 for all _lms with di}erent values of x 9 :tC considered in this work[ ร 0887 The Franklin Institute[ Published by Elsevier Science Ltd 0[ Nomenclature a constant A function of dimensionless time b B function of dimensionless distance d C thermal propagation speed C p speci_c heat