The UCSC Microbial Genome Browser is a window on the biology of more than 300 microbial species from Bacteria and Archaea domains. Basic gene annotaiton is derived from NCBI Genbank/RefSeq entries, with overlays of sequence conservation across multiple species, nucleotide and protein motifs, non-coding RNA predictions, operon predictions, and other types of bioinformatic analyses. In addition, we display available gene expression data, and soon, high-throughput RNA sequencing. Direct contributions of functional genomic data or bioinformatic analyses are welcome.