Induction of the Mycobacterium tuberculosis dosR gene, which is known to respond to hypoxia, was measured using RTq-PCR following exposure to different stresses. Increased expression was seen after exposure to S-nitrosoglutathione (GSNO), ethanol and (to a lesser extent) H₂O₂, but not heat- or cold-shock. We also demonstrated that hspX, which is dependent on dosR for expression, is induced when cultures are left standing for 30min, while significant but minor induction was seen following a 10min centrifugation. Microarray analysis was used to compare gene expression in wild-type and ΔdosR strains following 30min standing. Fifty-two genes were significantly up-regulated, and 19 genes were down-regulated. These included genes that had previously been reported as being part of the dosR regulon, and also some novel ones.