Studies with germ-free chicks and antimicrobial compounds have indicated the significance of the interaction between host nutrition and the intestinal microflora. This interaction has suddenly leapt to prominence as a result of the decision of the European Union to remove several antibacterial agents from use in animal feed. A consequence of this decision has been a loosening of some of the constraints on intestinal bacterial growth rates which will benefit from the use of slowly digested ingredients, because undigested feed is a potential substrate for bacterial fermentation. The use of poorly digestible ingredients runs the risk not only of poor performance, which has always been the case, but now there is an additional danger from bacterial overgrowth and subsequent disease/intestinal disorders. Variations in the nutritional quality of the ingredients are therefore of increased relevance, and any measures that reduce such variations are likely to be of benefit. As a result, the use of enzymes, which are known to reduce variations in the performance of birds fed on barley-, wheat- and maize-based diets, will need to be revisited, particularly with reference to correct dosage. In the past the use of antibiotics effectively reduced the need to consider enzyme use and dose. Coccidiosis control is also of great interest because of its association with necrotic enteritis. Prevention of coccidiosis and limitation of the damage to the intestines associated with this disease is of paramount importance if necrotic enteritis is subsequently to be avoided. As a result, the use of coccidiostats for direct control and betaine and other pronutrients for amelioration of the symptoms is receiving greater attention. Ultimately it is hoped that nutritional control will lead to microbiological control, allowing for more consistent production responses in the absence of antibiotics.