Emerging research has demonstrated that the sex hormone estradiol regulates fear extinction in female rodents and women. Estradiol may also regulate fear extinction in males, given its role in synaptic plasticity in both sexes. Here we report that inhibition of estradiol synthesis during extinction training, via the aromatase inhibitor fadrozole, significantly impairs extinction recall in male rats. This deficit in extinction recall is not due to state-dependent memory formation and is completely abolished by coadministration of estradiol. Our data suggest that estradiol may be just as important in the regulation of fear extinction in males as it is in females.