The mycotoxin ochratoxin A is a potent nephrotoxin and a possible human carcinogen. It occurs in a variety of plant products, including wine, grape juice and dried vine fruits. Several surveys have shown that the range of ochratoxin A contents detected in wine produced in Europe varied between 0.01 and 3.4 micro g/litre. Both incidence and concentration of the toxin were higher in wines from southern regions and increased in the order white<rose<red. In Italy, field trials were conducted in 1999 and 2000 to study fungi associated with grapes and their ability to produce ochratoxin. Aspergillus and/or Penicillium strains were present on grapes, starting from setting in a few vineyards. The highest level of grape colonization was found at early veraison in 1999 and at ripening in 2000. In both years, 95% of strains belonged to the genus Aspergillus. A. niger aggregate was dominant, with about 50% of the ochratoxin-positive strains identified as A. carbonarius. Other authors have confirmed the relevance of these fungi and underlined the contribution of A. carbonarius to the ochratoxin contamination of wine. This species is very invasive and colonizes and penetrates berries, even without skin damage. It emerges that temperature, rain and relative humidity are the main factors that influence ochratoxin production in grapes.