LAUSR

Abstract This paper is devoted to the existence of a periodic solution for ϕ-Laplacian neutral differential equation as follows (ϕ(x(t)−cx(t−τ))′)′=f(t,x(t),x′(t)). $$\begin{array}{} (\phi(x(t)-cx(t-\tau))')'=f(t,x(t),x'(t)). \end{array}$$ By applications of an extension of Mawhin’s continuous theorem due to Ge and Ren, we obtain that given equation has at least one periodic solution. Meanwhile, the approaches to estimate a priori bounds of periodic solutions are different from the corresponding ones of the known literature.