We discuss the role coarse-grained models play in investigating collective phenomena in bilayer membranes and place them in the context of alternative approaches. By reducing the degrees of freedom and applying simple effective potentials, coarse-grained models can address the large time scales and length scales of collective phenomena in membranes. Although the mapping from a coarse-grained model onto chemically realistic models is a challenge, such models provide a direct view on the phenomena that occur on the length scales of a few tens of nanometers. Their relevance is exemplified by the study of fusion of model membranes. (C) 2003 Wiley Periodicals, Inc.