Electronic Journal of Differential Equations, Conference 07 (2001), pp. 71-88. Title: A two dimensional Hammerstein problem The linear case. Authors: Jun Hua (West Virginia Univ., Morgantown, WV, USA) James L. Moseley (West Virginia Univ., Morgantown, WV, USA) Abstract: Nonlinear equations of the form $L[u]=\lambda g(u)$ where $L$ is a linear operator on a function space and $g$ maps $u$ to the composition function $g\circ u$ arise in the theory of spontaneous combustion. We assume $L$ is invertible so that such an equation can be written as a Hammerstein equation, $u=B[u]$ where $B[u]=\lambda L^{-1}[g(u)]$. To investigate the importance of the growth rate of $g$ and the sign and magnitude of $\lambda $ on the number of solutions of such problems, in a previous paper we considered the one-dimensional problem $L(x)=\lambda g(x)$ where $L(x)=ax$. This paper extends these results to two dimensions for the linear case. Published July 20, 2001. Math Subject Classifications: 47H30. Key Words: Hammerstein problem; nonlinear differential equation.