A case report is presented in which continuing root formation occurred in a carious nonvital and immature mandibular second premolar after single-visit calcium hydroxide apexification treatment. An apical hard tissue barrier was formed, accompanied by a separate, mesioapically growing root, 7 months posttreatment. Treatment was concluded with gutta-percha root canal restoration. The success of this single-visit apexification treatment supports the contention that frequent changing of the calcium hydroxide dressing is not always required to induce apical closure.