Electronic Journal of Differential Equations, Vol. 2005(2005), No. 44, pp. 1-16. Title: Existence of positive solutions to nonlinear elliptic problem in the half space Authors: Imed Bachar (Faculte des Sciences de Tunis, Tunisia) Habib Maagli (Faculte des Sciences de Tunis, Tunisia) Malek Zribi (Faculte des Sciences de Tunis, Tunisia) Abstract: This paper concerns nonlinear elliptic equations in the half space $\mathbb{R}_{+}^{n}:=\{ x=(x',x_{n})\in \mathbb{R}^{n}:x_{n}>0\} $, $n\geq 2$, with a nonlinear term satisfying some conditions related to a certain Kato class of functions. We prove some existence results and asymptotic behaviour for positive solutions using a potential theory approach. Submitted December 20, 2004. Published April 14, 2005. Math Subject Classifications: 34B27, 34J65. Key Words: Green function; elliptic equation; positive solution