Two-component regulatory systems serve to control gene expression in response to environmental and physiological changes. They are widespread among a variety of organisms and most often found in prokaryotes. One of the gram-positive microorganisms Bacillus subtilis is a well-studied bacterium whose complete nucleotide sequence has been determined. Thus, it is now possible to study transcription of the whole genome with microarray analysis. In this review we summarize the recent progress in B. subtilis two-component regulatory systems by describing the known systems and those for which the function was recently assigned. Also included is an attempt to construct a partial transcriptional network involving several two-component systems. The studies described here are based on the data from traditional genetics and biochemistry, and from microarray analysis of 29 two-component systems.