Summary. A chicken embryo cDNA library was screened with a mouse probe for ornithine decarboxylase (ODC) and 14 positively hybridizing clones isolated. The longest of these (1.7 kb) was sub-cloned and sequenced. It is estimated that the clone comprises approximately 98% of the coding region for chicken ODC. The DNA sequence shows 78% identity with the human ODC cDNA sequence and the deduced amino acid sequence is almost 90% homologous to mouse and human. Both the peptide and cDNA sequences show interesting potential regulatory features which are discussed here.