This study was undertaken to evaluate the effects of regular endurance-type exercise on glucose tolerance and glucose-stimulated insulin response (GSIR) in ovariectomized (OVX) rats with and without estrogen replacement. To do that, OVX Sprague-Dawley rats were compared with an OVX estradiol-treated group (OVXE2) and a sham-operated (Sham) group. Each of these groups was subdivided into a sedentary and a treadmill-trained (8 wk) group. Intravenous glucose tolerance tests (0.5 g/kg) were conducted in all rats 48 h after the last training session. Plasma levels of 17-estradiol and the uterus weight were significantly (P < 0.05) lower in OVX compared with results in Sham and significantly (P < 0.01) higher in OVXE2 (hyperestrogenic) compared with results in Sham. Body weights were significantly (P < 0.01) different among groups, in the following decreasing order: OVX, Sham, and OVXE2. The average daily food intake was significantly (P < 0.01) increased in OVX rats compared with Sham, whereas estradiol treatment diminished this effect (P < 0.01). Exercise training was found to alter none of the above-mentioned variables in all three experimental conditions. Although the mean integrated area under the glucose and insulin curves was not affected by OVX, training induced a significant (P < 0.01) reduction in the mean integrated area under the insulin curve in all three experimental conditions. It is concluded that the positive effects of physical training on improving GSIR in OVX and hyperestrogenic animals are similar to what has been found in Sham.