Groups of chickens were experimentally infested with equal doses of embryonated Ascaridea eggs. Birds were treated with a single oral dose of 100, 200, or 400 ug/kg. b.w. at 12th day (tissue phase) or 40th day-post infection (mature worms). The drug was uneffecient in controlling larval stages in tissue phase. All doses prooved to be highly effective against mature worms and lead to 95-100% elemination of the mature worm. A small dose of 100 ug/kg. b.w. is recommended, repeating of the dose is essential for elemination of infection.