This comprehensive evaluation of the Dynamic Indicators of Basic Early Literacy Skills Sixth Edition (DIBELS6) set of measures gives a practical illustration of signal detection methods, the methods used to determine the value of screening and diagnostic systems, and offers an updated set of cut scores (decision thresholds). Data were drawn from a sample of 13,507 English-proficient students in kindergarten through Grade 3, with more than 4,500 students per grade level. Results indicate that most DIBELS6 measures accurately predict comprehensive test performance and that previously published decision thresholds for DIBELS6 are generally appropriate with some key exceptions. For example, the performance of phoneme segmentation fluency did not always meet expectations. The revised DIBELS6 decision thresholds can satisfactorily identify students who may require additional supports.