The yeast enzyme phenylacrylic acid decarboxylase (PAD) confers resistance to phenylacrylic acids. Cinnamic acid (CA)-sensitive mutants lacking PAD activity were isolated and the PAD1 gene was cloned by phenotypic complementation. The nucleotide sequence of the smallest complementing fragment was determined. The predicted 242-amino-acid PAD polypeptide is 48.6% identical to the product of dedF of Escherichia coli. PAD activity and CA resistance, but not steady-state PAD1 mRNA levels, are influenced by mitochondrial genotype. PAD1 is a single-copy gene in the yeast genome and not essential for viability. The PAD1 locus was physically mapped to a position approx. 140 kb from the left end of chromosome IV.