SummaryThere is currently no simple and morbidity-free procedure available to determine opiate dependence in patients. There is preliminary evidence, however, that the naloxone conjunctival test may be useful in this regard. This test consists of instilling a drop of saline solution of naloxone hydrochloride (an opiate-receptor antagonist) into the subject's eye. This causes significant homolateral mydriasis (anisocoria) in the eye of a chronic opioid-dependent subject and not in that of a non-dependent subject. We reviewed the international literature on the naloxone conjunctival test using the Medline database and a manual search of major scientific journals specialized in the field of substance abuse. Up to March 1995, we identified six articles dealing specifically with the use of opiate antagonist ophthalmic solutions in populations of chronic opioid addicts. Four of the articles reported the occurrence of mydriasis when a solution of naloxone is used in opioid addicts. Two of the articles reported that there was no differential change in pupil size when the naloxone solution is used; however, one study used a much weaker and the other a much stronger solution of naloxone than reported in the other studies. From our review of the literature, it appears that the naloxone conjunctival test holds great promise as a simple and morbidity-free method of testing for chronic opioid addiction and, therefore, it should be studied further and its usage eventually developed.