The cross-cultural applicability of criteria for the diagnosis of substance use disorders and of instruments used for their assessment were studied in nine cultures. The qualitative and quantitative methods used in the study are described. Equivalents for English terms and concepts were found for all instrument items, diagnostic criteria, diagnoses and concepts, although often there was no single term equivalent to the English in the languages studied. Items assuming self-consciousness about feelings, and imputing causal relations, posed difficulties in several cultures. Single equivalent terms were lacking for some diagnostic criteria, and criteria were sometimes not readily differentiated from one another. Several criteria--narrowing of the drinking repertoire, time spent obtaining and using the drug, and tolerance for the drug--were less easy to use in cultures other than the United States. Thresholds for diagnosis used by clinicians often differed. In most cultures, clinicians were more likely to make a diagnosis of drug dependence than of alcohol dependence although behavioural signs were equivalent. The attitudes of societies to alcohol and drug use affects the use of criteria and the making of diagnoses.