The effects of the administration of the kappa agonist dynorphin1-17 and/or the kappa antagonist MR-2266-BS on ethanol preference was investigated using a paradigm by which rats develop alcohol preference. Administration of dynorphin shortly before or after the conditioning session (forced ethanol exposure) failed to affect later ethanol preference. However, dynorphin treatment prior to the first choice session reduced ethanol preference during the three consecutive testing days. This effect was reversed by the simultaneous administration of the kappa antagonist MR-2266-BS. The results of the present study provide further support for evidence of the involvement of dynorphinergic systems on drinking behavior and suggest that kappa-type opioid mechanisms may be involved in the consumption and development of preference to ethanol in rats.