The UCSC Archaeal Genome Browser is a window on the biology of more than 100 microbial species from the domain Archaea. Basic gene annotation 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 (microarray or high-throughput RNA sequencing). Direct contributions or notices of publication of functional genomic data or bioinformatic analyses from archaeal research labs are very welcome.