ABSTRACT. The purpose of this note is to indicate some applications of a new fixed point theorem to the question of periodic solutions of nonlinear autonomous functional differential equations. The techniques developed give the standard periodicity examples in the literature and some new results, notably for the neutral case, which do not seem accessible by previous methods.1. If X is a Banach space and A is a bounded subset of X, define y (A), the measure of noncompactness of A 9 to be inf{d > 0:A has a finite covering by sets of diameter less than d). This is a notion due to C. Kuratowski
) y(cö(A)) = y(A) and (2) y(A + B) <. y (A) + y(B). It is trivially true that (3)y(AvB) = max{y(A%y(B)}.For applications it is sometimes convenient to generalize the above idea slightly. If ju is a function which assigns to each bounded subset A of X a real number fi(A\ we say that \x is a generalized measure of noncompactness if ii satisfies properties (1), (2)