Electronic Journal of Differential Equations, Vol. 2009(2009), No. 21, pp. 1-9. Title: Mild solutions for semilinear fractional differential equations Authors: Gisele M. Mophou (Univ. des Antilles, Guadeloupe) Gaston M. N'Guerekata (Morgan State Univ., Baltimore, MD, USA Abstract: This paper concerns the existence of mild solutions for fractional semilinear differential equation with non local conditions in the $\alpha$-norm. We prove existence and uniqueness, assuming that the linear part generates an analytic compact bounded semigroup, and the nonlinear part is a Lipschitz continuous function with respect to the fractional power norm of the linear part. Submitted October 28, 2008. Published January 23, 2009. Math Subject Classifications: 34K05, 34A12, 34A40. Key Words: Fractional differential equation.