The effect of the selective delta-opioid antagonist ICI 174,864 (N,N-bisallyl-Tyr-Aib-Aib-Phe-Leu-OH: Aib=alpha-aminoisobutyric acid) on the hyperphagia induced by 2-deoxy-D-glucose (2-DG) was investigated in non-deprived rats. The increase in food intake produced by 2-DG (500 mg/kg i.p.) was not reduced by ICI 174,864 at a dose (3 micrograms/rat i.c.v.) which totally abolished the feeding response to the delta-agonist D-Ala2-D-Leu5-enkephalin (10 micrograms/rat i.c.v.). These findings suggest that the appetitive effects of 2-DG are not mediated by an enkephalinergic/delta-receptor system. They do not, however, preclude the possible involvement of endogenous opioids acting at other sub-types of opioid receptor in this glucoprivic ingestional response, which is suppressed by less specific opioid antagonists such as naloxone.