Research was conducted to determine whether individual ergot alkaloids could induce signs of fescue toxicosis. Nine Angus heifers received single i.v. injections of ergotamine tartrate, ergonovine maleate, and saline vehicle in a simple cross-over design. Each heifer received a different compound each week and all treatments during the study. Physiological traits measured 15 min before and 30, 60, and 90 min after treatment were respiration rate, rectal and skin temperatures, systolic and diastolic pressures, and heart rate. Blood samples were collected 5 min before and 105 min after treatments to assess plasma prolactin concentrations. Heifers were on a fescue-free diet in drylot. Ambient temperature averaged 35 degrees C during data collection. A treatment x time interaction existed (P < .05) for respiration rate and prolactin concentrations. Ergot alkaloids altered (P < .05) all traits across time, except rectal temperature. Heifers under the influence of ergot alkaloids exhibited significantly lower skin temperature, heart rate, and prolactin and had higher respiration rate and blood pressure. Results indicated that individual ergot alkaloids administered i.v. induced signs of fescue toxicosis in cattle.