In this paper we consider the existence of periodic solutions of neutral fu
nctional differential equations. It has been proved that for convex neutral
functional differential equations of D-operator type with finite (or infin
ite) delay and hyperneutral functional differential equations with finite d
elay, there is a periodic solution if and only if there is a bounded soluti
on. The results proved by Massera, Chow and Makay are generalized.