The aim of this study was to evaluate the physiological responses of Santa Ines and its crossbreeds with Suffolk races and Ile de France in Piracicaba, Brazil. Eighteen ewes were used assigned to a completely randomized design in a factorial diagram (3 x 3, 3 breed group: Santa Inês (SI); ½ Santa Inês + ½ Suffolk (Su x SI), and ½ Santa Inês + ½ Ile de France (Ile x SI) and 3 times of observation: 07:00, 13:00 and 19:00 hours) with 6 repetitions. The ewes were used to evaluate: rectal temperature (RT), superficial temperature (ST), eardrum temperature (ET) and respiratory frequency (RF). The ST showed difference (P<0.05) among genetic groups, being Ile x SI the group that showed the lower mean at 07:00 and the greater at 13:00. For the ET the Santa Inês presented the lower mean (P<0.05) than the others, at 13:00 and 19:00. The group Su x SI was greater RT (P<0.05) than SI. The lowest RT was registered at the morning. There was no difference (P>0.05) between the 13:00 and the 19:00. The crossbreeding Ile x SI show greater heat tolerance than Su x SI.