In the present work the existence of sex differences (Experiment 1) on the acquisition and extinction of a continuously reinforced response in a short and narrow runway (100 x 9 x 10 cm) were investigated. In addition to the investigation of the basic sex differences in Experiment 1, the effect of postpuberal gonadectomy of male and female rats and the role of the early postnatal gonadal steroids on these situations were also examined in Experiments 2 and 3, respectively. In all experiments, no sex differences were found in acquisition. However, males extinguished faster than female rats. Gonadectomy of both sexes in adulthood, although it increases their latencies in acquisition, did not affect the differences between sexes during extinction. In contrast, in Experiment 3 female androgenization and male orchidectomy on day one after birth reversed the direction of sex differences found between control rats in the extinction period. Our findings suggests that the observed sex differences in extinction may be due to an underlying sexual dimorphism in the response inhibition process.