Fenbendazole 4% (Panacur, Hoechst) administered in feed was used to treat chickens infected with Ascaridia galli, Heterakis gallinarum and Railletina spp. It was also used to treat Syngamus trachea in broiler birds. There was a marked drop in helminth egg counts in the faeces on the second day of treatment and the faeces became negative by the seventh day after the last treatment. Post-mortem examination 15 to 21 days later showed that the drug was 100% effective against Ascaridia galli and Heterakis gallinarum at 10 mg/kg. However, for complete removal of Railletina spp. 15 mg/kg was required. Similarly 20 mg/kg fenbendazole was effective against Syngamus trachea. It was concluded that fenbendazole is suitable for the treatment of the important intestinal and tracheal worms of poultry, a dose of 15 to 20 mg/kg for 3 consecutive days being recommended for use under field conditions.