The promoter of the 14 kb mRNA encoding the brain isoform of dystrophin in the mouse has been isolated and partially characterized. Unlike the promoter of the muscle dystrophin isoform, it does not contain a TATA box or other consensus sequences characteristic of the proximal region upstream of the cap sites of eukaryotic genes. Yet, it has a major initiation of transcription start site located 266 bp upstream from the first ATG which is in frame with the dystrophin coding sequence. The 5' untranslated region contains nine additional ATG triplets which are not in-frame with the coding sequence or are followed by stop codons. A DNA fragment extending from bp -1149 to +11 is sufficient to activate a reporter gene lacking a promoter in transfected neuroblastoma cells.