The Bacillus subtilis glpD gene, encoding glycerol-3-phosphate (G3P) dehydrogenase, is preceded by a promoter and an inverted repeat which is located between the promoter and the glpD coding region. The inverted repeat acts as a transcriptional terminator in vitro. Expression of glpD is induced by G3P in the presence of the glpP gene product. Full-length glpD transcripts can be detected only in glycerol-induced cells. The major glpD transcript is initiated from the glpD promoter but minor amounts of larger transcripts, possibly initiated at upstream glp promoters, can also be found. In uninduced cells short transcripts are present, corresponding to initiation at the glpD promoter and termination at the inverted repeat. Upon induction, these short transcripts disappear and are replaced by full-length glpD transcripts. The 3'-ends of full-length glpD transcripts were mapped to an inverted repeat located immediately downstream of glpD. These results show that glpD of B. subtilis is regulated by termination/antitermination of transcription.