So far, impromptu translation has only been perceived as a marginal phenomenon and has often been treated as a stepchild in university education. This book aims to remedy this situation: the hybrid form is described in its variants, defined, and compared with other forms of translation from a communication theory and cognitive linguistics perspective. The comparison of the impromptu performance of translators and interpreters using the language pair French-German sheds light on the specific difficulties involved. The competencies required for successful impromptu translation are compiled, and a didactic guide is developed for acquiring the skills that provide added value for translation and interpreting.