The growth of Byssochlamys nivea and P. granulatum was reduced by ochratoxin A (1 ppm, 10 ppm), whereas Aspergillus ochraceus growth and toxinogenesis were not affected by 1 and 10 ppm of patulin. When Penicillium granulatum and Asperigillus ochraceus were placed in the same medium the former grew and produced its toxin and ochratoxin production by the latter was weakened. Since patulin and ochratoxin can be found in the same substrate; the toxinogenic significance of in vitro strains is questionned.