<jats:p>The genes encoding succinate dehydrogenase <jats:italic>(sdhCDAB)</jats:italic>, the specific components of the 2-oxoglutarate dehydrogenase complex (ODH, E1o and E2o; <jats:italic>sucAB</jats:italic>) and succinyl-CoA synthetase <jats:italic>(sucCD)</jats:italic> form a cluster containing two promoters at 16 · 3 min in the chromosome of <jats:italic>Escherichia coli: P<jats:sub>sdh</jats:sub> sdhCDAB-P<jats:sub>suc</jats:sub> sucAB-sucCD</jats:italic>. The gene encoding the lipoamide dehydrogenase component of both the 2-oxoglutarate and pyruvate dehydrogenase complexes (E3; <jats:italic>IpdA</jats:italic>) is the distal gene of another cluster containing two promoters located at 2 · 7 min: <jats:italic>P<jats:sub>pdh</jats:sub> pdhR-aceEF-P<jats:sub>Ipd</jats:sub> IpdA</jats:italic>. The responses of the suc and <jats:italic>Ipd</jats:italic> promoters to different environmental conditions and to regulator defects were investigated with appropriate <jats:italic>IacZ</jats:italic> fusions, in order to understand how expression of the <jats:italic>sucAB</jats:italic> genes is co-regulated with other genes in the <jats:italic>sdhCDAB-sucABCD</jats:italic> cluster and with <jats:italic>IpdA</jats:italic> expression. Expression from the <jats:italic>suc</jats:italic> promoter was repressed by IHF and partially activated by s<jats:sup>38</jats:sup> but it was not regulated by ArcA, FNR, CRP, FruR or Fis, and not repressed by glucose or anaerobiosis, indicating that the well-established catabolite and anaerobic repression of ODH synthesis is imposed elsewhere. In contrast, the <jats:italic>Ipd</jats:italic> promoter was repressed by both glucose (via a CRP-independent mechanism) and anaerobiosis (mediated by ArcA), and activated by Fis, but it was not regulated by FNR, FruR, IHF or s<jats:sup>38</jats:sup>. These observations support the view that transcription of the <jats:italic>sucABCD</jats:italic> genes is primarily initiated and regulated at the upstream <jats:italic>sdh</jats:italic> promoter, and that the <jats:italic>Ipd</jats:italic> promoter is independently co-regulated with <jats:italic>P<jats:sub>sdh</jats:sub> </jats:italic> (primarily by ArcA-mediated repression) rather than with <jats:italic>P<jats:sub>suc</jats:sub> </jats:italic> <jats:sub>suc</jats:sub> Direct evidence for co-transcription of the entire <jats:italic>sdhCDAB-sucABCD</jats:italic> region from <jats:italic>P<jats:sub>sdh</jats:sub> </jats:italic> was obtained by detecting a 10 kb transcript in <jats:italic>rnc</jats:italic> and <jats:italic>rne</jats:italic> mutants, but not in the parental strains. Three RNaseIII-specific processing sites, which contribute to the extreme instability of the readthrough transcript, were identified in the <jats:italic>sdhCDAB-sucABCD</jats:italic> intergenic region. Other sites of endonuclease processing were located by interpreting the patterns of transcript subfragments observed in Northern blotting.