Two hundred and forty-nine deaths owing to substance overdose were reported to the Medico-Legal Centre, Dammam, Saudi Arabia in the 8 year period from 1990 to 1997. All cases were subject to a full forensic autopsy with toxicological and histological studies. The overall male:female ratio was 7.9:1 and males predominated in all age groups. Saudis outnumbered other nationalities and accounted for 191 (77%) of the cases. Four main categories of overdose fatalities were identified: opiates, prescribed medication, alcohol and carbon monoxide. Opiates accounted for 116 (47%) of all overdose deaths, although such fatal overdoses have been decreasing since 1993. Medically-prescribed drugs accounted for 50 (20%) of the fatalities (21 deaths from antidepressants, 19 from tranquillisers, five from hypnotics, three from paracetamol and two from amphetamines). Ethyl alcohol accounted for 27 deaths (11%) and carbon monoxide for 26 deaths (10.5%). This study shows a sharp fall in overdose fatalities in eastern Saudi Arabia during the last 5 years, which probably reflects the influence of a combined policy of strict legislations against drug trafficking and tight control over prescription of drugs.