DNA sequences affecting the transcription of the Escherichia coli rnpB gene encoding M1 RNA have been examined. Sequence analysis of the upstream region of the rnpB gene identified three regions homologous to the E. coli consensus promoter sequence. The promoter region of the rnpB gene was cloned into the galactokinase expression vector and galactokinase activity directed by the rnpB promoter was analyzed. Only the nearest promoter P-1 directed the synthesis of galactokinase. The overall effect of the upstream promoter homologies, P-2 and P-3 was not significant. DNA sequences derived from within the M1 RNA structural gene also affected synthesis of galactokinase directed by the rnpB promoter. The terminator region of the rnpB gene was serially deleted and cloned into the galactokinase expression vector. The relative galactokinase activities from the fusion plasmids were measured to estimate the efficiency of terminators T1, T2, and T3. The major termination occurred at the first terminator, T1.