Electronic Journal of Differential Equations, Vol. 1997(1997), No. 06, pp 1-11. Title: On a mixed problem for a coupled nonlinear system Authors: M. R. Clark (Univ. Federal da Paraiba, Brasil) O. A. Lima (Univ. Estadual da Paraiba, Brasil) Abstract: In this article we prove the existence and uniqueness of solutions to the mixed problem associated with the nonlinear system $$ u_{tt}-M(\int_\Omega |\nabla u|^2dx)\Delta u+|u|^\rho u+\theta =f $$ $$ \theta _t -\Delta \theta +u_{t}=g $$ where $M$ is a positive real function, and $f$ and $g$ are known real functions. Submitted November 26, 1996. Published March 6, 1997. Math Subject Classification: 35M10. Key Words: Mixed problem; nonlinear system; weak solutions; uniqueness.