First Author: Jacques Th\'evenaz e-mail: Jacques.Thevenaz@ima.unil.ch Address: Institut de Math\'ematiques, Universit\'e de Lausanne, CH--1015 Lausanne, Switzerland Second Author: Peter Webb email: webb@math.umn.edu Address: School of Mathematics, University of Minnesota, Minneapolis MN 55455 Title: Simple Mackey Functors Abstract: We classify the simple Mackey functors, via a discussion of certain adjoint constructions. We also show that when the group order is invertible, Mackey functors are semisimple. Journal: Proc. of 2nd international group theory conference, Bressanone (1989), Supplement to Rendiconti del Circolo Matematico di Palermo 23 (1990), 299-319.