M theory on orientifolds of K3xS1

We present several orientifolds of M theory on K3xS1 by additional projections with respect to the finite Abelian automorphism groups of K3. The resulting models correspond to anomaly-free theories in six dimensions. We construct explicit examples which can be interpreted as models with eight, four, two, and one vector multiples and N=1 supersymmetry in six dimensions. copyright 1996 The American Physical Society