In this article the authors evaluated the posttraumatic stress disorder (PTSD) Checklist's (PCL) psychometric properties in 142 older adult primary care patients screened for several psychiatric disorders. Several established PCL scoring rules were assessed. Receiver operating characteristic analyses revealed a PCL score of 37 achieving optimal sensitivity and specificity, when compared to the PCL's algorithm-derived PTSD diagnosis (based on whether at least one reexperiencing, three avoidance/numbing, and two hyperarousal symptoms were endorsed with a rating of 3 or higher, indicating at least moderate severity). Among depressed, anxious, and substance abusing older adults, the PCL demonstrated adequate internal consistency. It also revealed similar convergence with the Center for Epidemiological Studies-Depression scale, found in previous research. Implications for using the PTSD Checklist with community-dwelling older adults in primary care are discussed.