Brucella melitensis is a facultative intracellular pathogen. The regM gene encodes a sensory transduction protein kinase in B. melitensis 16M, and genes orthologous to regM have been found to exist in many bacterial species. However, little is known about the regulation function of this gene in Brucella. In order to characterize this gene, we constructed a marked deletion mutant of regM as well as its complemented strain. The mutant was less able to withstand acid and hyperosmotic conditions than wild-type strain but shown no significant difference with wild-type strain when challenged by elevated temperature and hypotonic conditions. In addition, inactivation of regM did not affect virulence in B. melitensis 16M in macrophage and mice infection models.