In this paper, we use the lower and upper solution method to obtain an existence theorem for the fourth-order boundary-value problem u((4))(t) = f(t, u(t), u'(t), u ''(t), u"'(t)), 0 < t < 1, u(0) = u'(1) = u ''(0) = 0, u'''(1) = g(integral(1)(0) u ''(t)d theta(t)), where f : [0, 1] x R-4 -> R, g : R -> R are continuous and may be nonlinear, and integral(1)(0) u ''(t)d theta(t) denotes the Riemann-Stieltjes integral.