To evaluate the incidence of fungi producing ochratoxin A in orange fruit and juice a survey was carried out by challenge test with ochratoxin A producing strains of Aspergillus westerdijkiae used as the model system. A. westerdijkiae grew into experimental lesions caused on orange surfaces, in orange natural medium and in orange juice and produced OTA in all environments. The higher temperature of 26 degrees C had a greater influence than temperatures of 20 degrees C and 4 degrees C on the growth of the mould, and OTA production. The environmental temperature of 20 degrees C, slows down but does not prevent toxin production. At the lowest temperature of 4 degrees C no growth was observed.