sporulation is a quorum sensing response and a cellular differentiation process regulated by signalling molecules and physiological and environmental signals. the regulation of sporulation initiation has been extensively studied in bacillus subtilis and occurs through phosphorelay. b. subtilis detects metabolic and environmental signals through histidine kinases that are autophosphorylated and then transfer the phosphate group to response regulators, activating the expression of sporulation genes. however, there are other important sporulated bacilli like those from the b. cereus group. b. cereus toxins are related to food-borne intoxication, b. anthracis may be used as biological weapon in bioterrorism, and b. thuringiensis is an excellent biological control agent. therefore, it is critical to understand the signalling processes that control sporulation initiation and the toxin synthesis. this review summarizes known literature about regulation of initiation of sporulation in the b. cereus group focusing in the role of histidine kinases and the putative open reading frames of these sensors in b. subtilis and b. thuringiensis. the genomes of the b. cereus group have 10 to 14 putative histidine kinases and 7 to 11 response regulators, compared to 6 histidine kinases and 6 response regulators in b. subtilis, implying that this last bacteria should have a lower capacity to respond to environmental and metabolic signals.