A 12-month criterion prevalence was assessed as part of the World Health Organization's Study on the Reliability and Validity of the Alcohol and Drug Use Disorder Instruments in various settings at eight sites around the world, using the Schedules for Clinical Assessment in Neuropsychiatry (SCAN). A majority of respondents were recruited from non-treatment settings. In addition to exploratory factor analysis, confirmatory factor analysis was used to analyze factor structures with weighted least square methods and tetrachoric correlation matrices. Multi-sample analysis techniques were used to model differences among drug classes. The full data analyses identified a single factor solution for each user population and across user populations; however, analyses of data from users who reported low to moderate symptomatology identified a two-dimensional construct among alcohol, cannabis, and opiate users that consisted of a major "dependence" factor and a lesser "abuse" factor. In addition, results showed that neither the abuse criterion (A2) use in physical hazardous situations or the dependence criterion (D7) use despite knowledge of psychological/physical problems were central to the latent construct in any of the user populations, except for D7 among alcohol users. The study concludes that the multidimensional results found among users with low to moderate symptomatology indicate that previous results from relatively homogeneous populations may have been biased toward lesser order solutions and that the DSM-IV substance disorder criteria describe at least two distinct phenomena, supporting the current DSM-IV organization of substance disorder criteria. Further work is required to evaluate whether prevalent symptoms are present in random or predictable combination, whether combinations reflecting a specific hierarchy of severity can be identified, and whether incident symptoms are accumulated in a predictable pattern within specific user populations and across user populations. 5 tables and 31 references