KEGG (Kyoto Encyclopedia of Genes and Genomes) is a bioinformatics resource for understanding the functions and utilities of cells and organisms from both high-level and genomic perspectives. It is a self-sufficient, integrated resource consisting of genomic, chemical, and network information, with cross-references to numerous outside databases, containing a complete set of building blocks (genes and molecules) and wiring diagrams (interaction networks) to represent cellular functions. This unit describes protocols for using KEGG, KEGG PATHWAY, KEGG GENES, KEGG SSDB, KEGG EXPRESSION, and KEGG LIGAND. Protocols are also described for how to color maps, compare chemical compounds and glycan chains, analyze Ortholog Clusters, and visualize and analyze microarray data, among other procedures. All of these many protocols enable the user to take advantage of the full breadth of the functionality provided by KEGG.