The MMPI scores of 353 forensic psychiatric patients were examined to determine the validity scale characteristics of this population. Frequency distributions are provided for L, F, K, F-K, and O-S. These findings suggest that traditional cutoffs for these scales are of questionable use in determining the validity of MMPI scores for this population. It is suggested that elevations on validity measures in this population may be due to characterological features, substance abuse, and the presence of acute psychopathology in addition to deliberate efforts to deceive. The validity and clinical scale characteristics of a small group of identified malingerers (n = 10) were compared to those of psychotic patients and were found to be distinctly different. Malingerers scored significantly higher on all “fake bad” validity measures (F, F-K, and O-S) and all clinical scales except 5 and 9, and lower on L and K. The clinical implications of these findings are discussed.