A survey was carried out to investigate the prevalence of nicarbazin residues in eggs in Northern Ireland. Nicarbazin, in the form of 4,4′-dinitrocarbanilide (DNC), was detected in 39 of the 190 eggs analysed. An experiment was designed to establish the relationship between nicarbazin-contaminated feed and nicarbazin residues in eggs. The concentrations of both the DNC and 4,6-dimethyl-2-hydroxypyrimidine (DHP) components of the drug in eggs were proportional to feed levels. The maximum feed nicarbazin concentration of 12.1mg/kg (8.6 mg/kg DNC and 3.5mg/kg DHP) gave rise to mean maximum whole egg concentrations of 631 μg/kg DNC and 51.8 μg/kg DHP. After withdrawal of the experimental diet, DNC was undetectable in eggs after 12 days and DHP after 3 days. Feed contaminated with nicarbazin at concentrations greater than about 2mg/kg gave rise to egg DNC residues at concentrations greater than the Differential Action L imit (DAL) set by the UK (100 μg/kg). DNC was contained almost entirely in the yolk of the egg, whereas DHP was distributed between albumen and yolk in a ratio of approximately 3:1.