Abstract Enzootic calcinosis associated with Nierembergia veitchii ingestion occurs in sheep in southern Brazil, and has been described as a chronic disease. However, in recent years this plant has been associated with cases of acute disease and sudden death in sheep. Data from 12 sheep flocks affected by this toxicosis in southern Brazil, between 1990 and 2007, are described. Thirty-five sheep were necropsied. Twenty-four had a history of chronic disease with weight loss, stiff gait, tucked abdomen, kyphosis, and recumbency. Eleven sheep died suddenly with no prior history of severe illness. In all affected sheep, gross changes included poor body condition and widespread mineralization of several tissues, more prominent in blood vessels and heart valves. In addition, sheep that experienced sudden death had moderate to severe pulmonary edema. There was a distinct seasonal pattern to the clinical presentations, with chronic disease occurring in spring and summer and the acute cases dying in fall and winter. Stress of parturition or poor climatic/nutritional conditions may have precipitated the acute deaths.