Abstract Objective—To compare the effects of the ergot alkaloid ergovaline with effects of ergotamine on blood pressure, heart rate, respiratory rate, and body temperature in conscious sheep. Animals—3 sheep with indwelling arterial catheters. Procedure—Ergotamine and ergovaline were injected IV (20 nmol/kg), and their effects on arterial blood pressure, heart rate, respiratory rate and pattern, body temperature, and skeletal muscle electromyographic activity were compared with control values obtained following injections of saline (0.9% NaCl) solution or acetone. Results—Both ergopeptides caused immediate and significant increases in blood pressure (50 to 75 mm Hg) without concomitant increases in heart rate. Ergovaline but not ergotamine significantly increased pulse pressure (35 mm Hg). Both ergopeptides resulted in decreased respiratory rate and increased respiratory depth within the first hour of administration. Body temperature was decreased slightly upon ergopeptide administration but continued to increase thereafter, with greater increases developing with ergovaline than with ergotamine. Increased body temperatures of 3.0 to 3.5 C were maintained for at least 10 hours. Respiratory rate was increased to rates as high as 210 to 220 breaths/min in association with hyperthermia. Ergopeptides had no effect on skeletal muscle electromyographic activity. Conclusions and Clinical Relevance—In sheep, ergovaline has similar effects to ergotamine on cardiovascular and pulmonary function and body temperature but is more potent. These effects are consistent with clinical signs observed in the toxicoses developed when ruminants ingest grass with high concentrations of ergopeptides. (Am J Vet Res 2002;63:387–393)