The reaction of the Baianinha orange (Citrus sinensis Osb.), a Brazilian hud sport of the Washington Navel, to applications of 2,4-D was studied at the Limeira Agr. Exp. Sta., São Paulo. All concentrations of this hormonial herbicide used in the tests induced some modifications of the normal characteristics of the plants when compared with the controls. The leaves, flowers, and fruits were the plant parts most affected by the treatments. Some of the morphological changes induced on the fruits tend to confirm the view that the Baia orange originated as a mutation from the Seleta variety. Data obtained on the yield, weight per fruit, and fruit drop indicate that application of 2,4-D on the Baianinha orange is not advisable under the conditions of the present experiment.