Transcriptional activation by p53 is dependent on the presence of a specific p53 binding site within control sequences of the target gene. One such target gene is the mouse muscle-specific creatine kinase (MCK) gene, which contains a p53 binding site between promoter residues -3182 and -3133 relative to the transcription start site. This DNA sequence is reported to be sufficient to confer p53-dependent activation on the MCK promoter. In contrast to this finding, evidence from promoter deletion studies suggests that sequences in the MCK promoter other than this p53 binding site also permit p53-dependent activation. To investigate this possibility, we have further examined sequences in the MCK promoter required for transcriptional activation by mouse p53. We report here identification of a second p53-responsive sequence within the MCK promoter. This novel sequence is situated between residues -177 and -81, and can confer p53-dependent, position- and orientation-independent activation on a heterologous promoter. Moreover, this sequence can specifically bind mouse and human p53. By promoter deletion studies, we provide evidence that these two elements cooperate to provide high-level, p53-dependent activation of the MCK promoter.