Mycotoxins are secondary metabolites produced by many genera of fungi in many commodities, under certain conditions. Mycotoxicological control of feed is a procedure that aims to protect human and animal health, avoiding the adverse effects of these undesirable substances. This component of the sanitary control of feed and food is essential to prevent the presence of those substances which can seriously affect the health of the animals. In Portugal, there is relatively few information related to the natural occurrence of mycotoxins in feed. In this context, the authors present results and data compilation concerning the occurrence of mycotoxins in raw materials and also feed for dairy cattle, swine, poultry, horses, fish, laboratory rats and pet; making a generic qualitative appreciation of the risks associated to the presence of mycotoxins in these feedstuffs. The mycotoxins studied: aflatoxins (AFs), ochratoxin A (OTA), fumonisin B1 and B2 (FB1, FB2) were analysed by High Performance Liquid Chromatoghraphy (HPLC). Deoxynivalenol (DON) and zearalenone (ZEN) were determined by Thin-Layer Chromatography (TLC). The results suggest that contaminations with these mycotoxins in feed are quite common, revealing the need for surveillance and monitoring programs for the prevention of the sanitary impacts of these "non desirable substances".