Two of the most widely used measures for the assessment of malingering in forensic populations are the Miller Forensic Assessment of Symptoms Test (M-FAST) and the Structured Interview of Reported Symptoms (SIRS). The underlying dimensions of the SIRS have been well established in the literature, but the structure of the M-FAST remains relatively untested. Understanding of its dimensions is critical for construct validity and guiding its proper use. Confirmatory factor analysis was used to provide evidence of a single parsimonious malingering factor to account for the covariation of the M-FAST items in a sample of 244 forensic patients. In addition, the model was cross-validated with an independent sample of 210 forensic patients. Finally, the M-FAST factor was modeled in conjunction with two factors of the SIRS. Results provide further validation of the underlying detection strategy found in the M-FAST. (Contains 2 tables and 3 notes.)