This study examined the sociodemographic and practice characteristics of psychiatrists whose caseloads consist primarily of patients with Substance Use Disorders (SUD). A. survey instrument was completed by a random sample of 865 psychiatrists. Study groups were defined as high-SUD providers if psychiatrists reported having 51% or more patients with SUD (n = 92) and non-SUD providers as those who reported not having any patients with SUD (n = 128). High-SUD providers tended to be younger, more likely to graduate from international medical schools, have larger caseloads, work more hours per week, and have a higher proportion of inpatients and publicly funded patients than non-SUD providers. Results suggest that psychiatrists who primarily treat patients with SUD are in their early careers and treat patients with more clinical, psychosocial, and economic disadvantages. The implications of these findings for psychiatry training programs and policy makers will be discussed.The proportion of patients with a specific mental disorder treated by psychiatrists may be associated with characteristics of the clinician and the clinical practice. Differences in practice characteristics may be due in part to the intrinsic clinical characteristics of the patient's diagnosis or extrinsic factors that may either predispose the patient to a particular disease or develop as a consequence of the disease. Intrinsic factors may include level of severity and disability produced by the disease. For example, psychiatric practices for severely drugdependent patients who exhibit significant symptoms of withdrawal, with immediate urgency for drug substitution and risk of becoming violent, may require emergency care services, possibly in residential settings and with an appropriate security system. In contrast, a psychiatric practice of patients with phobic disorders may require a more supportive milieu and a behavioral plan to treat the specific phobia.Extrinsic predisposing factors may include local epidemiological trends, socio-cultural and economic factors, and type of health insurance coverage. Extrinsic consequences of the disease may include changes in socio-economic status, stigmatization, discrimination, unemployment, loss of health insurance coverage, and involvement in the criminal justice system, among others. Epidemiological studies have shown that the prevalence of abuse or dependence on various types of substances is not uniformly distributed across the US. Cocaine, heroin, and other illicit drug use tends to be more prevalent in urban than rural communities, 1 methamphetamine abuse is more common on the West Coast, 2 and heroin dependence is more prevalent in the Northeast. 3,4 Similarly, quantity and type of SUD treatment services are not uniformly distributed across the country. Certain areas have more numerous and diverse services, offering residential versus outpatient treatment, methadone maintenance versus drugfree only, SUD separate from mental health treatment or linked through common providers, etc. For examp...