Eight cases of chlorodyne dependence seen in a London drug clinic are described. These cases and the results of an inquiry among pharmacies in central and south London suggest that this form of drug dependence is commoner among younger people than has been supposed and that the total number of chlorodyne-dependent people in Greater London may exceed 1,000. The prognosis for cure is poor. We recommend that the supply of chlorodyne, now available without prescription to the public, should be restricted.