4-methylimidazolc (4-MeI) has until now been the only identified toxic compound in ammoniated forage considered to be of possible etiological significance in ammoniated forage poisoning. However, several authors have concluded that 4-MeI alone cannot explain the toxicity observed (Morgan & Edwards 1986, Nielsen et al 1986, Motoi et at. 1997). On this background, we have examined samples of ammoniated forage and of milk, plasma, and urine collected from ewes and lambs during a previous experimental poisoning study (Sivertsen et al. 1993). We have also studied similar samples from a Norwegian Red Cattle dairy cow fed ammoniated hay for the first 5 days after calving. We have, in addition to the previously known ingredients 4-MeI and 2-methylimida-zole (2-MeI), identified 5 new compounds in these samples, all of which were found to be di-alkylsubstituted imidazoles: 1,2-dimcthylimi-dazole (1,2-diMeI), 1,4-dimethyl imidazole (1,4-diMeI), 1,5-dimethyl imidazole (1,5-diMeI), 2,4-dimethylimidazole (2,4-diMeI) and 2-ethyl, 4-methylimidazole (2Et-4MeI) (Muller et al. 1998). In this paper we present quantitative measurements of these di- and monoalky 1 imidazoles in a selection of the collected samples.