Malingered mental illness is a concern within a prison in part because it results in the diversion of services and funds from legitimately mentally ill persons to those malingering for secondary gain. The M-FAST is designed to determine whether an inmate is so malingering. It is a 25-item structured interview in which all but 3 of the items require the examinee to verbalize response options. The test can be administered in approximately 5 minutes. The Structured Interview of Reported Symptoms (SIRS) is currently being used to detect malingering, but it requires between 30 and 45 minutes to administer. In the current study the SIRS was administered to classify participants as malingerers or non-malingerers. The M-FAST is designed so that malingerers will score significantly higher than honest responders on the total score as well as on the individual scales. This study found that SIRS-defined malingerers scored significantly higher on the M-FAST total and scale scores. Consistent with previous M-FAST validity research, the utility results showed accurate classification was best achieved with an M-FAST total cutoff score of 6 (positive predictive power equals .78, and negative predictive power equals .89). Utility analyses across race produced almost identical results, indicating that the M-FAST is generalizable for African-American, Hispanic, and Caucasian inmates. 7 tables, 4 figures, and 31 references