Technical Abstract: Ten yearling steers weighing 270-360 kg were acutely poisoned and died after eating Lupinus argenteus (silvery lupine) containing high levels of piperidine alkaloids, including ammodendrine and N-methylammodendrine. The plant was in the early seed pod stage when the cattle started grazing lupine. The range on which the cattle were grazing was moderately depleted dof good quality grasses. This reduced availability of quality feed was considered a major contributing factor in causing the cattle to start grazing lupine. Proximate analysis of whole plant, seed pods and seed, revealed crude protein levels of 16.4%, 19.4% and 48%, respectively. Alkaloid analysis of the whole plant, and individual plant parts such as seed and seed pods (30-40% seed shatter) revealed total alkaloid levels ranging from 0.70-2.5% (0.70-2.5 mg/100mg plant) dry weight. Ammodendrine levels ranged from 0.24% in seed pods with >70% seed loss to 1.35% in early ygrowth plant with no seed. N-methylammodendrine levels ranged from 0.38% in seed pods with >70% seed shatter to 1.04% in pure seed. Other minor alkaloids were not specifically identified but comprised a combined total of 0.08% in seed pods with >70% seed shatter to 0.60% in early growth plant before seed pod formation. It is estimated that these cattle would have eaten over 1.8 gm/kg dry weight (486 gm to 648 gm) of lupine in a 24 hour period to be lethal. We believe this is the first report of acute poisoning and death losses in cattle associated with a piperidine alkaloid- containing lupine and specifically with Lupinus argenteus.