Phalaris spp. grasses are useful pasture components but have been associated with neurological and sudden death intoxication syndromes. Despite agronomic development of Phalaris spp. to produce "low -toxicity" cultivars, outbreaks of intoxication have continued to occur. These outbreaks could result from a combination of poorly understood environmental or animal factors exacerbating the effect of the low concentration of known toxic alkaloids. Alternatively, previously unrecognised alkaloids could have intrinsic toxicity. Recent investigations have revealed the presence of the cardioactive N -methyltyramine in P. aquatica cultivars, and alkaloids of unknown toxicity i.e., the oxindoles coerulescine and horsfiline, and the furanobisindole phalarine, in P. coerulescens cultivars. The structures of coerulescine and phalarine were determined using NMR spectroscopy and mass spectrometry.