THE ANALYSIS OF MULTIGRID ALGORITHMS FOR NONCONFORMING AND MIXED METHODS FOR SECOND ORDER ELLIPTIC PROBLEMS Zhangxin Chen Department of Mathematics and Institute for Scientific Computation, Texas A&M University College Station, TX 77843--3404 Do Y. Kwak Department of Mathematics, Korea Advanced Institute cience and Technology, Taejon, Korea 305--701 Abstract. In this paper we consider multigrid algorithms for nonconforming and mixed finite element methods for second order elliptic problems on triangular and rectangular finite elements. We prove optimal convergence properties of the W-cycle multigrid algorithm and uniform condition number estimates for the variable V-cycle preconditioner. Lower order terms are treated, so our results also apply to parabolic equations.