The behaviors and attributes of 503 Scottish injecting drug users were modeled using the linear structural equations program LISREL. Drug use was directly related to prison experience, sexual activity, sharing of injecting equipment, and prostitution. Although the prevalence of HIV among the sample was low (2.0%), the pattern of risk behaviors observed in the data affords potential for future spread of the virus. Harm reduction measures taken by injectors in response to the threat posed by AIDS were inversely related to drug use but, more encouragingly, directly related to awareness of the disease, treatment for drug use, and prostitution.