Anticoccidial efficacy of a drug combination containing monensin at 8 p.p.m. plus the new antioxidant duokvin at 120 p.p.m. in the feed was compared with that of monensin alone at the recommended level of 100 p.p.m. against a field isolate of the coccidium Eimeria acervulina Tyzzer, 1929 in a battery study. Both monensin and monensin duokvin combination were effective against E. acervulina when judged by weight gain, feed conversion and faecal scores. There was no significant difference in the chemoprophylactic activity of either treatments. Neither monensin at 100 p.p.m. nor the combination proved effective in terms of oocyst production. In accordance with the earlier findings with E. lenella, the combination seems appropriate for field trials.