This study was concerned with the similarities and differences between different groups of drug users. It examines social norms in each group, including group attitudes and concurrent drug use behaviour and considers changes over time. In-depth semi-structured interviews were carried out within each of seven distinct social groups of drug misusers. identified by using the snowballing method. Within the sample as a whole, extent of drug experience and severity of drug dependence were inversely correlated with age of first drug use. and positively correlated with a number of measures of poor self-care and antisocial behaviour. The qualitative data were examined for themes to distinguish between groups of drug users. The major themes to emerge were: drug misuse behaviours and patterns of misuse: social relationships: attitudes to drug misuse; and attitudes to risks and problems. Three homogeneous groups were identified from similarities and differences in these themes: young experimental users, moderate social users, and heavy chaotic users. These groups differed in their drug experience and in their expectations of future use. The similarities in drug use behaviour within groups and differences between groups indicate that social group membership may well influence individual attitudes and behaviour. The significance of these findings for policy and practice are considered.