This article discusses the Critical Period Hypothesis (CPH) as it relates to the naturalistic acquisition of foreign-language (L2) pronunciation by adults and children. An examination of the existing empirical and theoretical literature leads to the conclusion that there is no conclusive support for the existence of a critical period for human speech learning, and that assuming a critical period does exist may inhibit the search for testable hypotheses concerning the basis for observed adult-child differences in L2 pronunciation. These conclusions are based on the existence of direct counter-evidence, as well as on the observation that apparent adult-child performance differences may arise from many different confounding factors other than adult-child differences in neurological maturation or organization that cannot be adequately controlled in behavioral research.