Technical Abstract: It has been estimated that tall fescue toxicosis reduces cattle production by hundreds of millions of dollars annually. Economic losses associated with tall fescue toxicosis can be reduced by the use of heat tolerant cattle. Previous data indicate that Senepol cattle are heat tolerant; however data evaluating the performance of Senepol cattle in a cow-calf operation where the dominant forage is tall fescue are hard to find. A study was conducted at Booneville, AR from 1997 to 1999 in which the cow-calf performance of Senepol dams were compared to that of Brahman and English (Angus/Hereford) cows grazing tall fescue continuously year-round. Percentage of cows exposed to the bull that weaned a calf in the following year was not significantly different (P>0.10) among the breeds and averaged about 90%. Weaning weights for calves (adjusted to 205 days postpartum) were significantly greater for Senepol cows, 241.3 kg per head. The average adjusted weaning weights for calves from Brahman and English breed cows were not significantly different, averaging 213.1 and 200.1 kg per head, respectively. Calves from Brahman and Senepol cows tended to gain weight at a constant rate throughout the spring and summer, whereas the rate of gain for calves from English breed cows declined towards weaning. Therefore, the decreased production of pounds of weaned calves with English breed cows on tall fescue was due to both a reduced rate of gain and a shorter duration of sustained gain. All cows lost body weight from January to weaning in the middle of October. These results indicate that Senepol cows tended to be more productive than other breeds of cattle in a cow-calf operation when the dominant forage was tall fescue.