<jats:title>Summary</jats:title><jats:p>A key step in the biosynthesis of macrolide antibiotics is the assembly of a large macrocyclic lactone ring by a multienzyme protein complex called the polyketide synthase. In the species <jats:italic>Streptomyces ambofaciens</jats:italic>, the polyketide synthase for the assembly of the 16‐membered ring of the macrolide antibiotic spiramycin is encoded by the biosynthetic gene <jats:italic>srmG.</jats:italic> Here we show that the accumulation of transcripts from the <jats:italic>srmG</jats:italic> promoter is governed by the regulatory gene <jats:italic>srmR</jats:italic>, whose predicted product, a 65 kDa polypeptide, is not significantly similar in its deduced amino acid sequence to that of previously reported proteins in the protein databases. The <jats:italic>srmR</jats:italic> gene product is also required for the accumulation of transcripts from <jats:italic>srmX</jats:italic>, an additional gene in the vicinity of <jats:italic>srmR</jats:italic>, but not for the accumulation of transcripts from <jats:italic>srmR</jats:italic> itself. Interestingly, mutations in <jats:italic>srmR</jats:italic> prevent the accumulation of transcripts from the spiramycin resistance gene <jats:italic>srmB</jats:italic>, but this is an indirect consequence of the failure of <jats:italic>srmR</jats:italic> mutants to produce spiramycin, which is an inducer of its own resistance gene. The possibility that <jats:italic>srmR</jats:italic> is the prototype for a new class of regulatory genes governing early events in the biosynthesis of macrolide antibiotics is discussed.