This thesis presents a framework for computer assisted language learning using a virtual language teacher. It is an attempt at creating, not only a new type of language learning software, but also a server-based application that collects large amounts of speech material for future research purposes.The motivation for the framework is to create a research platform for computer assisted language learning, and computer assisted pronunciation training.Within the thesis, different feedback strategies and pronunciation error detectors are exploredThis is a broad, interdisciplinary approach, combining research from a number of scientific disciplines, such as speech-technology, game studies, cognitive science, phonetics, phonology, and second-language acquisition and teaching methodologies.The thesis discusses the paradigm both from a top-down point of view, where a number of functionally separate but interacting units are presented as part of a proposed architecture, and bottom-up by demonstrating and testing an implementation of the framework.