The reaction to stress can generate the Cannon reaction whether the animal is submitted to stressing stimulus. A chronic stressing stimulus generates an increase of the adrenals in morphological terms, since the stress affect the hormonal and others systems via neural influence, however, no one study was performed to verify the effects of the subacute stress on the adrenal size. Therefore, the main this study was to verify the alterations of the adrenal size comparing two groups of Wistar rats submitted and not submitted to swimming stress. The results demonstrate that occurred an increase of the adrenals in the animals submitted to the pool with water in relation to animals submitted to the pool without water with significant statistical difference. In conclusion, the subacute stress is enough to generate a morphological alteration in the adrenals in Wistar rats.