Synthetic zeolites (NaX, NaY, NaA, and CaA) were evaluated in vitro for their ability to sorb aflatoxin (AF) B1 from an aqueous solution. Zeolite NaA (ZN) was selected to be tested in vivo because of its high affinity and its stable association with AFB1. This sorbent was incorporated into diets (1%) containing 2.5 mg/kg AFB1. Male broiler chicks from 21 to 42 d of age received ad libitum access to their respective diets and water. When compared with controls, BW gains were lower (P < 0.05) for broilers that were fed AF in their diets. No differences were found between the BW gains of chicks fed diets without AF and those of chicks fed AF + ZN, indicating almost total protection against the effects caused by AF. Liver weights were considerably higher in chicks fed a diet containing AF, compared with those of controls, nevertheless, no significant differences were found in feed:gain ratio among the groups. The findings of this research suggest that ZN can counteract some of the toxic effects of AF in growing broiler chicks.