OBJECTIVE To determine the activity of cortisol in rats treated with exogenous adrenocorticotropic hormone (ACTH) and a resveratrol supplement. METHODS Forty-eight adult female rats and 16 male rats of the strain (Rattus norvegicus) that were three months old and with body weights ranging from 200 to 250 g for females and 300 to 350 g for males were used and kept in controlled environmental conditions: temperature of 20±2° C and light-dark cycles of 14 and 10 hours. They were fed a balanced diet and had free access to water. The rats were randomly divided into four groups: group 1 - was treated with 5 µg/kg of ACTH i.p. every twelve hours; group 2 - received the same treatment with ACTH plus a grape extract supplement (resveratrol) of 40 mg/kg; group 3 - only received grape extract (resveratrol); and group 4 - received a saline solution (0.9%) i.p. and oral, and served as controls. The experimental design was a 2×2 factorial with two levels ACTH and two polyphenol levels (grape extract). RESULTS No significant differences were found in blood cortisol concentrations, by day and gender, or by treatment effects (0.75 µg/dL ± 0.11; p <0.001). CONCLUSIONS Results suggest that chronic stress and consumption of resveratrol did not directly alter levels of plasmatic cortisol in either stressed or unstressed rats. It was concluded that the given dosage levels of ACTH possibly did not produce sufficient stimulation of the adrenal gland for these animals.