The antibiotics used in the treatment of mastitis are very effective inhibitors of starter culture organisms. When very small amounts of these antibiotics get into the milk supply, the milk is unfit for use. There is no practical method by which the dairy plant Operator can overcome the presence of these “wonder drugs.” A comprehensive education program must be instituted to inform the dairy farmer of the dangers of allowing these antibiotics to get into the milk supply. He must be taught methods of avoiding this hazard. This program must be accompanied by legal action when necessary.