The literature review indicates prevalence rates ranging from 9 percent to 47 percent vary according to where, when, and who was tested. Other drugs, most commonly marijuana, benzodiazepines, and cocaine, follow a pattern similar to alcohol. The optimum method of measuring substance use depends on the goal of the assessment, and a combination of clinical, self- report, and biochemical markers is recommended. Simple screening questions should be routinely used by emergency room and trauma unit staff and further assessment should be conducted when high- risk factors have been identified. Such risk factors include males, younger patients, metropolitan centers, after midnight and on weekends, injury from violence, accidents, high acuity, and psychiatric morbidity. Further, screening should be complemented by intervention, referral, and treatment for those in need. 60 references and 1 table