Electronic Journal of Differential Equations, Vol. 2000(2000), No. 51, pp. 1-17. Title: Gradient method in Sobolev spaces for nonlocal boundary-value problems Author: J. Karatson (Eotvos Lorand Univ., Budapest, Hungary) Abstract: An infinite-dimensional gradient method is proposed for the numerical solution of nonlocal quasilinear boundary-value problems. The iteration is executed for the boundary-value problem itself (i.e. on the continuous level) in the corresponding Sobolev space, reducing the nonlinear boundary-value problem to auxiliary linear problems. We extend earlier results concerning local (Dirichlet) boundary-value problems. We show linear convergence of our method, and present a numerical example. Submitted November 29, 1999. Published June 30, 2000. Math Subject Classifications: 35J65, 46N20, 49M10. Key Words: nonlocal boundary-value problems; gradient method in Sobolev space; infinite-dimensional preconditioning.