A transcript analysis of the citrate synthase and succinate dehydrogenase genes (gltA-sdhCDAB) of Escherichia coli was done by nuclease S1 mapping. Evidence was obtained for two monocistronic gltA transcripts extending anti-clockwise, to a common terminus, from independent promoters with start points 196 bp (major) and 299 bp (minor) upstream of the gltA coding region. Evidence was also obtained for two polycistronic sdh transcripts, sdhCDAB (minor) and sdhDAB (major), extending clockwise, from sites 219 bp upstream of sdhC and 1455 bp upstream of sdhD (i.e. within sdhC), to a common terminus. The synthesis of all of the transcripts was repressed by growth in the presence of glucose, and this is consistent with the well-established fact that both enzymes are subject to catabolite repression. Sequences resembling known binding sites for the cAMP-CRP (cyclic AMP-cyclicAMP receptor protein) complex occur in the vicinity of each promoter suggesting that they are activated by the cAMP-CRP complex.