The paper describes a comprehensive and objective evaluation of 2358 persons arrested in Philadelphia for driving while intoxicated. It was demonstrated that 63.8% of this population was involved with alcohol to an extent that a diagnosis of alcoholism was evident, and it is suggested that these persons are in need of intensive treatment to prevent further dependency on alcohol. It is significant that these persons were diagnosed as suffering from alcoholism because they had been arrested for DWI and referred for evaluation. They are considered to offer an excellent opportunity for early intervention of what might be a progressive disease process. The study utilizes four parameters on which a diagnosis of serious alcohol impairment is established. They are the blood alcohol concentration at the time of arrest, the quantity and frequency of alcohol intake, the behavior associated with the drinking, and the Eysenck Personality Inventory, which measures the degree of neuroticism found in these subjects. Problems in the establishment of a diagnosis of alcoholism in this particular population are presented, and the need for measurement with several instruments is emphasized. Through use of the techniques described, it is possible that specific treatment directions can be established based on particular patterns of alcoholism.