Zeolites are crystalline, hydrated aluminosilicates of alkali and alkaline earthcations which have infinite, three dimensional structure. Among many propertiesattributed to zeolites, two most characteristics that relates to theireffectiveness in animal nutrition are their ability to lose and gain waterreversibly and being capable of exchanging selectively a variety of cations intheir structure without much major changes of structure. However the effect ofzeolites on food intake, weight gain, growth rate, egg production, egg weight,shell thickness and internal egg characteristic are in dispute. While some ofthe experiments report beneficial effect due to inclusion of zeolite in the dietof birds, others show no changes and yet there are results that indicate thenegative effects. Reasons such as level of usage, type of zeolite (naturalvs. synthetics) and even within naturalones, the levels of impurities, are to be blamed for discrepancies reported fromthe experiments. On the other hand there has been evidence that zeolites hasbeneficial effect on feed efficiency ratio, water consumption, nutrientutilization, manure and litter condition and more importantly onaflatoxicosis.