In this review, the problem of viral contaminations in animal cell culture will be presented with special emphasis on animal cell technology used for the production of biologicals for prophylaxis and therapy. In addition, this article will suggest actions which can be taken, in order to assure the absence of viral contaminations. These may include the use of production media devoid of animal derived substances, validation of viral clearance in downstream processing or analytics for detecting adventitious viruses in cell culture and final biological product.