'Substance Use Disorders' represents a diagnostic subgroup in which ICD-10 and DSM-IV agree in most generalities and many particulars. Both systems' use disorders are based on the 'dependence syndrome' construct by Edwards and Gross and include a large and overlapping set of substance-induced syndromes. Differences at the category level are limited to DSM-IV 'abuse' vs. ICD-10 'harmful use', elimination of 'pathological alcohol intoxication' from DSM-IV and inclusion of substance-induced 'sexual dysfunctions and sleep disorders' in DSM-IV, but not in ICD-10. Cross-system reconciliation would entail few conceptual compromises but many criterion changes. Before embarking on a reconciliation process, the benefits of a common, world-wide nomenclature must be weighed against the many costs of changing either system. Even small changes can yield large differences in rates, reduce comparability across data gathered with different systems and incur considerable costs related to clinician retraining, changes in record keeping and changes in diagnostic interview schedules. Moreover, empirical data can have limited impact on the choices between the two systems because findings are either absent or equivocal, particularly for differences at the criterion level. Nevertheless, more research is needed particularly to examine the comparative reliability and validity of abuse and harmful use diagnoses.