Electronic Journal of Differential Equations, Vol. 2003(2003), No. 15, pp. 1-14. Title: A multiplicity result for a class of superquadratic Hamiltonian systems Authors: Joao Marcos do O (Univ. Fed. Paraiba, Brazil) Pedro Ubilla (Univ. de Santiago de Chile, Chile) Abstract: We establish the existence of two nontrivial solutions to semilinear elliptic systems with superquadratic and subcritical growth rates. For a small positive parameter $ \lambda $, we consider the system $$\displaylines{ -\Delta v = \lambda f(u) \quad \hbox{in } \Omega , \cr -\Delta u = g(v) \quad \hbox{in } \Omega , \cr u = v=0 \quad \hbox{on } \partial \Omega , }$$ where $\Omega$ is a smooth bounded domain in $\mathbb{R}^N$ with $N\geq 1$. One solution is obtained applying Ambrosetti and Rabinowitz's classical Mountain Pass Theorem, and the other solution by a local minimization. \end{abstract} Submitted May 15, 2002. Published February 14, 2003. Math Subject Classifications: 35J50, 35J60, 35J65, 35J55. Key Words: Elliptic systems; minimax techniques; Mountain Pass Theorem; Ekeland's variational principle; multiplicity of solutions.