We designed PCR primers hy comparison of the deduced amino acid sequences of several ornithine decarboxylase (ODC) genes. They were used to amplify fragments homologous to these genes from several dimorphic fungi. These were sequenced and the deduced amino acid sequences were compared with the corresponding regions of ODCs from different sources, Fungal ODCs fell into a compact group, well separated from the ODCs of other taxa, Sequence homology among fungal enzymes corresponded to their taxonomic position, Interesting patterns of amino acid conservation in ODCs from fungi, distinct from other organisms, were detected.