Electronic Journal of Differential Equations, Vol. 2001(2001), No. 24, pp. 1-14. Title: Existence results for a class of semi-linear evolution equations Author: Eduardo Hernandez M. (Univ. de Sao Paulo, Sao Carlos, SP, Brazil) Abstract: We prove the existence of regular solutions for the quasi-linear evolution $$ {d \over dt}(x(t)+g(t,x(t))=Ax(t)+f(t,x(t)), $$ where $A$ is the infinitesimal generator of an analytic semigroup of bounded linear operators defined on a Banach space and the functions $f, g$ are continuous. Submitted December 14, 2000. Published April 10, 2001. Math Subject Classifications: 35A05, 34G20, 34A09. Key Words: Banach spaces; semigroup of linear operators; abstract differential equations; fractional powers of closed operators; regular solutions.