In this article, we concerned with oscillation of the neutral delay differential equation [x(t) − px(t − τ)]′ + qx(t − σ) = 0 with constant coefficients. By constructing several suitable auxiliary functions, we obtained some necessary and sufficient conditions for oscillation of all the solutions of the aforementioned equation for the cases 0 < p < 1 and p > 1.

For a neutral functional differential equation with a stable operator, D, it is shown that the solution operator is the sum of a contraction and a completely continuous operator.