A method is presented for the simultaneous determination of the three ionophores, monensin, salinomycin and narasin in muscle, liver and eggs from domestic fowl. Samples are homogenised in methanol and any ionophores present are extracted into toluene-hexane. The extracts are concentrated and injected into a bench-top electrospray LC-MS system. Chromatography is carried out using an end-capped reversed-phase column, with a mobile phase consisting a mixture of acetonitrile, methanol, tetrahydrofuran, trifluoroacetic acid and water. Using single-ion monitoring, the ionophores can be detected down to the 1 ng/g level.