In recent years there has been much research activity concerning the oscillation of solutions of delay differential equations. To a large extent, this is due to the realization that delay differential equations are important in applications. New applications which involve delay differential equations continue to arise with increasing frequency in the modelling of diverse phenomena in physics, biology, ecology, and physiology. In this book, we are concerned with the oscillation criteria of solutions of the second-order neutral differential equations. The book contains several and remarks illustrative examples as an application of our results. The obtained results essentially improve many known results in the literature.