EN
This paper considers the generalized Henon-Heiles system, defined by the Hamiltonian Η = (p^{2}_{1} + p^{2}_{2} + Αq^{2}_{1} + Bq^{2}_{2})/2 + Cq^{2}_{1}q_{2} + Dq^{3}_{2}. Melnikov's method is used to prove the existence of nondegenerate homoclinic orbits near two integrable cases: (o) C = 0; A, B, D arbitrary; (i) A = B; C = 3D. The existence of such orbits precludes the existence of analytic second integrals.