Aflatoxin (AF) and clinoptilolite (CLI, a natural zeolite) were added to broiler food and some biochemical values and enzyme activities were evaluated. The experimental design consisted of six dietary treatments. (1) Control: basal diet; (2) CLI: basal diet plus 15 g clinoptilolite kg-1 diet; (3) 50 ppb AF: basal diet plus 50 μg total aflatoxin (AF; the composition given below) kg-1 diet; (4) 50 ppb AF + CLI: basal diet Plus 50 μg AF Plus 15 g CLI kg-1 diet; (5) 100 ppb AF: basal diet plus 100 μg AF kg-1 diet; (6) 100 ppb AF + CLI: basal diet plus 100 μg AF Plus 15 g CLI kg-1 diet. A commercially available CLI was provided from the west region of Turkey and its chemical formula is "KNa2Ca2(Si29AL7)O · 72 · 32H2O". For this a total of 576 1-day-old Ross broiler chicks were housed in six treatment groups from days 1 to 42. AF treatment significantly increased the serum Na levels and the aspartate-amino-transferase (ASAT) and alanine-amino-trasferase (ALAT) enzyme activities, while total protein, albumin, total cholesterol uric acid, and K levels were not significantly different between groups. These results suggest that these low AF levels in food did not change the serum biochemistry but significantly affected the enzyme activities in broilers. © 2002 Elsevier Science Ltd. All rights reserved.