Computer databases, networks and software tools are essential materials and methods for biomedical research and are involved in almost every aspect of disease gene mapping and positional cloning. Public databases of DNA and protein sequences and genetic and physical map information are increasing rapidly in size and complexity and are also improving in quality, comprehensiveness, interoperability and access. A new generation of software tools for navigating through the biomedical literature has become available. Programs for sequence homology searching and genetic map construction have become more sophisticated, yet easier to use. Global computer networks are bringing state-of-the-art capabilities to all.