Bioluminescence levels comparable to those achievable in Escherichia coli have yet to be obtained from luxAB expression in gram-positive bacteria. In this communication we describe the gene engineering required to generate a highly bioluminescent derivative of Bacillus subtilis. The combination of a powerful promoter, P(xyn), a fusion derivative of luxAB from Vibrio harveyi and translational coupling have overcome the previously reported limitations in luxAB expression. The implications for highly bioluminescent gram-positive organisms are discussed.