The development of effective antidotes against organophosphates such as dichlorvos has been a persistent challenge over the past decades. Therapy of organophosphate poisoning is based on the administration of atropine and oxime as standard antidotes. The present study was undertaken to evaluate the ability of sodium bicarbonate to improve protective effects of standard antidotes in rats poisoned with dichlorvos. The aim of this experiment was to establish the correlation between protective effects and biochemical parameters relevant for acid-base status. In order to examine the protective effect of both standard antidotes and their combinations, groups of experimental animals were poisoned subcutaneously with increasing doses of dichlorvos. Immediately thereafter, rats were treated with atropine 10 mg/kg intramuscularly, oximes 10 mg/kg intramuscularly and sodium bicarbonate 3 mmol/kg intraperitoneally. These antidotes were administered either as single doses or in combinations. In the biochemical part of the experiments, rats were poisoned with dichlorvos 1.3 LD(50) (10.64 mg/kg) subcutaneously and immediately thereafter treated with atropine 10 mg/kg intramuscularly, oximes (trimedoxime or obidoxime) 10 mg/kg intramuscularly and sodium bicarbonate 3 mmol/kg intraperitoneally either as single doses or in combinations. Parameters relevant for acid-base status were measured 10 minutes after the administration of antidotes. The results of our study indicate that addition of sodium bicarbonate to standard antidotes significantly improves protective effects of atropine, obidoxime and trimedoxime. Correlation between protection and biochemical outcome is clearly evident when sodium bicarbonate is being added to atropine.