Ponderosa pine needles cause abortion and a poorly described toxicosis when eaten by cattle. In previous trials, the abortifacient compound of pine needles was identified as isocupressic acid. At abortifacient doses, isocupressic acid caused no other toxicosis. However, other pine needle fractions, similar in composition to several commercially available rosin products, caused no abortion but were very toxic. The purpose of this study was to describe the toxicoses of ponderosa pine, compare its toxicity with other rosin and related pine products, and identify the toxin. Four groups of three pregnant beef cows each were treated with either ponderosa pine tips, rosin gum, dehydroabietic acid, or ground alfalfa. The cows treated with pine tips aborted, had retained placentas with endometritis, and developed both renal and neurologic lesions. The cattle treated with rosin gum or dehydroabietic acid did not abort but developed similar signs and lesions of intoxication. Clinical signs of intoxication included anorexia, mild rumen acidosis, dyspnea, paresis progressing to paralysis, and death. Clinical biochemical results, suggestive of renal, hepatic, and muscular disease, included azotemia, hypercreatinemia, hyperphosphatemia, proteinuria, and marked elevations of various serum enzymes. Histologically, all poisoned animals had nephrosis, vacuolation of basal ganglia neuropil with patchy perivascular and myelinic edema, and skeletal myonecrosis. The alfalfa-treated controls were normal. These findings suggest that ponderosa pine needles and tips are both abortifacient and toxic. Because the lesions caused by pine tips, rosin gum, and dehydroabietic acid are similar, toxicosis is most likely due to the diterpene abietane acids, common in all three.