How to understand what procedure is due as a fundamental or constitutional right may have a critical impact on designing a civil procedure. Using comparative law and empirically oriented methodologies, I study how procedural due process is understood in national and international jurisdictions. Based on those findings, I argue that non-criminal matters in general, and civil matters in particular, require a theoretical basis on which to address the question: what are the basic requirements of due process, as distinct from conceptions that originate in criminal justice?