The nucleotide sequence of a complete cDNA copy of enkephalin precursor mRNA from human phaeochromocytoma is reported. The corresponding amino acid sequence shows that the precursor is 267 amino acids long and contains six interspersed Met-enkephalin sequences and one Leu-enkephalin sequence. Five of the seven enkephalins are flanked on both sides by pairs of basic amino acid residues. The precursors does not contain the sequences of the opioid peptides, dynorphin, alpha-neo-endorphin or beta-endorphin.