- Bayesian networks are weighted directed acyclic graphs (DAGs). Layout of DAGs has been studied for many years, with variants of the horizontal layering algorithm of Sugiyama et al. (Sugiyama, Tagawa & Toda 1981) the preferred approach for medium size graphs. Following Gansner et al. (Gansner, Koutsofios, North & Vo 1993) we extend the classic horizontal layering algorithm with an additional vertex coordinate assignment phase which is designed to remove overlap between vertices with non-zero width and height. This is required because vertices in the Bayesian network are typically large and may vary greatly in height and width so a major component of good layout is to place vertices closely together without overlap. Our main contribution is to describe and evaluate a variety of novel techniques for vertex coordinate assignment.