Preliminary testing of the K6 scale with three offender samples found rates of serious mental illness in the expected range of 15-20 percent. The average time for administering the K6 was less than 3 minutes, and only 2 of more than 260 participants could not complete the form on their own because of language problems. Because of its brevity and ease of use, K6 can be used in the current screening practices of many criminal justice institutions. Despite the clear need and legal requirements for mental health services to offenders, many criminal justice organizations have failed to provide them. An important factor in this failure is the lack of a screening tool for quickly and reliably identifying symptoms of severe mental illness in offenders entering the criminal justice system. A promising screening tool to meet this need has recently been tested. The K6 scale was developed by Ronald Kessler, it contains six core items whose scoring reveals symptoms of serious mental illness. Respondents are asked to indicate on a scale of one to four how often they have experienced each of the following in the past 30 days: nervousness, hopelessness, restlessness, being depressed to the extent that nothing helped "cheer you up," experiencing everything as an effort, and worthlessness. Individuals who have cumulative scores of 13 and above are in the upper 10 percent of the general population in terms of symptoms of serious psychological distress associated with serious mental illness. 1 table, 1 figure, and 4 notes