This is a preliminary study of the socio-demographic characteristics and pattern of substance abuse in the eastern region of Saudi Arabia. Clinico-statistical analysis of 116 patients was based on the Diagnostic and Statistical Manual for Mental Disorder, Third Edition, Revised (DSM-III-R) definitions of drug abuse, a semi-stuctured psychiatric interview and examination, and laboratory investigations. Eighty-three percent of the patients were below the age of 32 years, 52.6% were unemployed and the majority were of intermediate education. Eighty-four percent of the patients abused heroin either alone or in combination with other drugs. Of the patients 31% used alcohol, 26% used cannabis, and 10% used stimulants. The use of other drugs was rare. Heroin abusers were younger with short duration and less polydrug abuse than alcoholics. In comparison with heroin abusers studied abroad, more of our patients were employed and drug use was more chronic, i.e., the mean duration of drug abuse was much longer.