The nucleotide sequence in the promoter region for the coat protein gene of phage fd has been determined. This sequence contains an endonuclease R-Hha cleavage site at the fifteenth nucleotide upstream from the RNA start site. Cleavage results in loss of promoter function. Comparison with the sequence of another fd promoter indicates that the longest sequence common to both was TATAAT in the region in which RNA polymerase forms a stable initiation complex.