The National Center for Genome Resources has released PathDB version 2.0, a research tool for scientists interested in analyzing their experimental or computational data in the context of biological pathways and networks. The software is both a data repository and a system for building and visualizing cellular networks. Uses include finding all pathways and phenotypes associated with genes in a cluster or validating computationally predicted associations with known biological data. Version 2.0 includes improvements in data modeling and data acquisition.