In this study we have determined the morphological, some physiological and biochemical characteristics of a fungal strain isolated from balsamic and cider vinegars. The examination of fungal contamination of 100 balsamic and cider vinegar samples showed that 90% contained more than 104 colony forming units (CFU ml-1), but in most samples (65%) values of more than 105 CFUml-1 were obtained. The most frequent contamination was with Monascus sp. (80% of the samples examined showed 2x103 to 6x105 CFUml-1). This mould can produce secondary metabolites such as citrinin and monacolin KL (lactone form), and monacolin KA (acid form). Using high-performance liquid chromatography (HPLC) with fluorescence detection, citrinin was found in 68% of the samples. The concentration of these mycotoxins varied between 1.6x10-2 g ml-1 and 7.2x10-2 g ml-1. The concentrations of citrinin were very low, and we can anticipate that this compound at these concentrations has no toxic effects on renal cells. Monacolin was not detected in any sample studied.