Recognized for nearly four decades, most juvenile suspects waive their Miranda rights and almost immediately provide self-incriminating evidence. Miranda-specific measures were eventually developed to understand their capacities and limitations. With extensive revisions, the Miranda Rights Comprehension Instruments (MRCI) were normed and validated. Beyond reliability, the current study addresses the convergent and discriminant validity of the MRCI. In response to Frumkin and Sellbom’s criticism of the MRCI’s norms, the current research provides representative data on 245 legally involved juveniles with percentiles to facilitate the interpretation of MRCI data. The current investigation is also the first MRCI study to link directly Miranda comprehension (i.e., the knowing prong) to Miranda reasoning (i.e., the intelligent prong) of waiver decisions.