Electronic Journal of Differential Equations, Vol. 2011 (2011), No. 12, pp. 1-9. Title: Existence of positive solutions for some nonlinear elliptic systems on the half space Author: Noureddine Zeddini (King Abdulaziz Univ., Rabigh, Saudi Arabia) Abstract: We prove some existence of positive solutions to the semilinear elliptic system $$\displaylines{ \Delta u =\lambda p(x)g(v)\cr \Delta v =\mu q(x)f(u) }$$ in the half space ${\mathbb{R}}^n_+$, $n\geq 2$, subject to some Dirichlet conditions, where $\lambda$ and $\mu$ are nonnegative parameters. The functions $f, g$ are nonnegative continuous monotone on $(0,\infty)$ and the potentials $p, q$ are nonnegative and satisfy some hypotheses related to the Kato class $K^\infty({\mathbb{R}}^n_+)$. Submitted March 16, 2010. Published January 21, 2011. Math Subject Classifications: 35J55, 35J60, 35J65. Key Words: Green function; Kato class; elliptic systems; positive solutions.