A method based upon polymerase chain reaction (PCR) for the detection of Phaseolus vulgaris beans in chestnut purée was developed. The method involves DNA isolation by the GeneSpin kit and PCR with primers oriented to a sequence of a nuclear gene encoding PvLEA-18, a late embryogenesis-abundant protein of beans. The PCR method was shown to be specific for Ph. vulgaris, producing a 100 bp fragment with six Ph. vulgaris cultivars, and negative results with four non- Ph. vulgaris Phaseolus samples and five non- Phaseolus legumes. When evaluated with model mixtures of Ph. vulgaris beans and the chestnut purée, a detection limit of 1% was determined.