The study provided evidence that the CODSI instruments showed sufficient value to justify their use for referring prisoners for further assessment and as a means of collecting mental health data in prison substance abuse treatment programs. Additional results validated the use of three standardized mental health screening instruments, the MHSF, the MINI-M, and the GSS in prison substance abuse settings as well as establishing the best cutoff scores for this purpose. The CODSI instruments showed sufficient value in terms of brevity and efficiency, and when combined with the Texas Christian University Drug Screen (TCUDS), resulted in a screening device for co-occurring mental and substance use disorders in prison substance abuse treatment programs. The study specifically determined that the six-item CODSI-MD accurately determined the presence of any mental disorder and the three-item CODSI-SMD demonstrated particular strength in determining the presence of a severe mental disorder. Both tests performed reasonably well and were comparable to the longer instruments in overall accuracy. The project was based on an initial pilot study and served as a validation study, employing a sample of 280 consecutive new admissions to prison substance abuse treatment programs. The results warrant future validation studies in other criminal justice populations and settings. The investigators plan a future study to assess the validity of the CODSI-MD and the CODSI-SMD in conjunction with the TCUDS as a screener for offenders entering prison. Limitations are discussed in detail. Tables, notes, references