Whole blood samples were collected from arrested D.U.I. subjects in the greater Pittsburgh area. The samples were analyzed for the presence of alcohol, cannabinoids, cocaine, barbituates and amphetamines using radioimmunoassay.All subjects were arrested for unsafe or reckless driving and had failed roadside sobriety testing before submitting to blood tests. Blood samples were taken by emergency personnel within fifteen minutes of arrest. The sample compliance in allowing blood samples to be drawn was 94%.The samples found 39% positive for Delta-9-THC and 5% positive for cocaine. The average blood alcohol content was .21%.