Information about the control of the activity of the 2-oxoglutarate dehydrogenase complex (OGDHC), a key enzyme in the citric acid cycle, is not well covered in the biochemical education literature, especially as it concerns the allosteric regulation of OGDHC by adenine nucleotide and ortophosphate. From experimental work published during the last 25 years, the following basic view is clear: (a) animal OGDHC is very sensitive to ADP, P[subscript i], and Ca[superscript 2+]; (b) these positive effectors increase the affinity of OGDHC to 2-oxoglutarate; (c) OGDHC is inhibited by ATP, NADH, and succinyl-CoA; (d) the ATP effect is realized mainly via opposition to ADP activation; (e) NADH, in addition to inhibiting the dihydrolipoamide dehydrogenase component of the enzyme complex (competitively "versus" NAD[superscript +]) decreases the affinity of 2-oxoglutarate dehydrogenase to its substrate; (f) bacterial and plant OGDHC are activated by AMP instead of ADP. These main effects form the basis of short term regulation of OGDHC. It is desirable that such information should reach biochemistry students.