In a polyethnic sample of 832 consecutive new outpatients attending a private psychiatric clinic in Dubai, drug and alcohol related problems were highly represented among nationals. Nationals constitute around 20% of the general population in Dubai and 47.7% of the whole patient population of the clinic but constitute 80.6% of all substance abuse cases. Substance abuse patients were mostly male, younger adults, less educated and more unemployed than other psychiatric outpatients. The study confirms earlier observations indicating higher substance abuse among nationals frequenting psychiatric services. Heroin-related problems are more common than alcohol-related problems in outpatients. A social causation hypothesis based on the stresses resulting from major socioeconomic changes during the latter three decades may explain these findings.