The crp gene of E. coli, which codes for cAMP receptor protein (CRP), has been cloned in the plasmid pBR322 on the basis of a genetic complementation. One of the recombinant plasmids, pHA1, was shown to direct the synthesis of CRP in a cell-free system. The location of the crp gene was determined by constructing subclones carrying various portions of pHA1. The nucleotide sequence of the crp gene has been determined. The coding region consists of 627 base pairs (bp), which specify a protein of 209 amino acids. The predicted amino acid sequence from the DNA sequence is consistent with the amino acid sequence partially known and the amino acid composition of CRP. After the coding region, there is a G-C rich inverted repeat sequence followed by a run of Ts, which could be a terminator of the crp gene. A possible promoter sequence was found about 180 bp upstream from the initiation codon and was shown to act as a promoter in vitro and in vivo. There are two dyad symmetry regions in a 167 bp leader sequence.