In the current investigation, the authors examined the validity of the L-r and K-r scales on the recently developed Minnesota Multiphasic Personality Inventory-2-Restructured Form (MMPI-2-RF; Y. S. Ben-Porath & A. Tellegen, in press) in measuring underreported response bias. Three archival samples previously collected for examining MMPI-2 validity scales were reanalyzed in 2 studies. In Study 1 L-r and K-r significantly differentiated 2 groups of participants (patients with schizophrenia and university students) who had been instructed to underreport on the MMPI-2 from participants who took the test under standard instructions. L-r and K-r also added incremental predictive variance to one another in differentiating these groups. In Study 2 a similar set of outcomes emerged through the use of a differential prevalence design in which L-r and K-r significantly differentiated a group of child custody litigants who were administered the MMPI-2 from university students taking the test under standard instructions. (Contains 4 tables and 3 footnotes.)