Outbreaks of Anagallis arvensis poisoning were observed from 1994 to 1998 in cattle and sheep in Uruguay during December and January. Cattle morbidity varied between 3.2 and 53.2% and lethality 42.6 and 100%. Sheep morbidity was 2.8 to 42.9% and lethality 81.3 to 100%. Nine outbreaks occurred on