A mutation in a gene dicA of Escherichia coli leads to temperature-sensitive cell division, by allowing expression of a nearby division inhibition gene dicB (1). We have now established the sequence of the DicA region and identified DicA as a 15.5 KD protein. A second gene dicC transcribed divergently from dicA and coding for an 8.5 KD protein can also complement mutation dicA1 when provided on a multicopy plasmid.