Intravenous injection of endotoxin fromEscherichia coli(0.01 μg and 0.1 μg per kg body weight), sodium nucleinate from yeast (5 mg and 10 mg per kg body weight) or Poly I: Poly C (15 μg and 30 μg per kg body weight) caused fever, changes in heart rate and stasis of the extrinsic ruminal contractions in conscious goats. It appears that ruminal stasis is associated with clinical and experimental fever. The febrile responses were abolished by the prior intravenous administration of flurbiprofen (2 mg per kg body weight), a potent non‐steroidal anti‐inflammatory and antipyretic agent. This agent, however, only had a partial antagonistic influence upon pyrogen‐induced ruminal stasis. The secondary changes in heart rate were not prevented by the drug. It seems unlikely that the inhibition of the extrinsic ruminal contractions by exogenous pyrogens is due simply to a release of prost