the objective of this study was to evaluate the effect of hyperthermia at the day of artificial insemination (ai) up to day 13th on reproductive performance of gilts and sows. in the experiment 1, 488 females were divided in two groups according to the rectal temperature: g1= ￡ 39.5oc (normothermia), and g2 = > 39.5oc (hiperthermia). the females having hyperthermia showed higher return to estrus rate (err), and lower farrowing rate (fr) and litter size (ls) (p<0.05) than females having normothermia. in the second experiment, 764 females were grouped in four groups: g1 = hyperthermia on the day of ai; g2 = hyperthermia on one of the first four days after ai; g3 = hyperthermia in one day of the first two groups, and, g4 = hyperthermia betwen 10-13th day of pregnancy. females having hyperthermia at the day of the first ai and during the first four days after ai, had a higher err and lower fr (p<0.01) in g1 and g2, and lower ls in g1, g2 and g3 (p<0.01), than the females with normothermia. there were not differences among the females havig hyperthermia or normothermia in g4. in the experiment 3, from 102 gilts, 88 were slaughtered from 29 to 34 days after ai. the err were higher (p<0.01)and the pregnant rate (pr) at up to 24 days, the number of viable embryos (nve) and the embryo survival rate (esr) were lower in females having hyperthermia (p<0.05). in conclusion, hyperthermia at the day of the first ai and during the first four days after ai can be deleterious to the female reproductive performance.