In this paper we present a new formulation for the nonlinear Cauchy problem for elliptic equations. This formulation allows us to give a method for solving this class of problems. The nonlinear problem is reduced to a linear Cauchy problem for the Laplace equation coupled with a sequence of nonlinear scalar equations. We solve the linear problem using the iterative method introduced in [7]. The linear dense systems obtained from a boundary element approximation are solved using an efficient implementation which accelerate the iterative process. Various types of convergence, comparison results and effects of small perturbations on boundary data are investigated. The numerical results show that the method produces a stable good approximate solution.