Two random samples of Danish prisoners on remand (solitary confinement (SC) and non-SC)) were examined using semistructured and standardized psychiatric and social interviews, cognitive tests, and questionnaires. Heroin dependence was divided into injection heroin dependence (IHD) and smoke heroin dependence (SHD). Comparisons corrected for confounders were made with regard to IHD versus SHD and dependent versus non-dependent subjects. Thirty-two per cent of the sample had lifetime heroin dependence, and the IHD versus SHD ratio was 3:1. The IHD subjects were more severely strained than SHD with regard to somatic complications (blood-transferred infections), early social strain, psychiatric comorbidity (mood disorders), personality dimensions (introversion), and cognitive performance (low performance scale score). The IHD subjects were considered more vulnerable than SHD subjects, both premorbid and during the dependence. SHD subjects may be recruited from other groups than the traditional (that is, IHD) ...