The first extremal point for a boundary value problem with impulse for an n
(th)-order linear, ordinary differential equation is characterized by the e
xistence of a nontrivial solution that lies in a cone. Cone theoretic argum
ents are applied to linear, monotone, compacts maps. To construct such maps
, an impulse effect operator is constructed to complement the usual Green's
function approach. An application is made to a nonlinear problem. (C) 2000
Elsevier Science Ltd. All rights reserved.