Despite high prevalence rates, many jails lack validated measures or consistent processes for detecting mental illness. In this study, we examined the utility of the K6, an internationally used brief mental health screening measure within an urban jail. The K6 and several other mental health measures were administered to 515 jailed women. The K6 identified 36% as having a serious mental illness. There was a high concordance with the other measures, particularly when using the highest level of symptom distress (top quartile) as the comparison. These findings are promising, particularly when other mental health screening tools have less success in detecting depression and trauma-related disorders among women. (Contains 4 tables and 2 notes.)