Expansion theorems, and related results, concerning nonlinear integral equations are proved, and are applied to systems of differential equations of the form

, almost all

continuous on

in which the solution

is

-vector valued. In particular, we show the existence of, and show how to obtain, a locally convergent expansion for

in terms of

, when certain reasonable conditions are met, including the condition that an associated system of linear differential equations is bounded-input bounded-output stable. The expansion converges in a normed space of bounded continuous

-vector valued functions defined on

, and involves terms that are sums of Volterra-like iterated integrals.