During the last years the testing and promoting of the competence in the languages of children of immigrants has become an interesting interdisciplinary domain and an important field of activity for the education policy in Germany. In the meantime, a great number of specific tests for investigating the competence of speech exist in Germany. Many of them have been evaluated on the basis of several methods. Most of them are characterized by an easy handling because performance and analysis can be done within a relatively short time. On the other hand, most of these procedures are not standardized and neglect theories of language development; moreover, they disregard the multilingual living conditions and the competence in languages of children. This can cause problems for the planning, the execution and effectiveness of the advancement. These difficulties could be avoided when bearing in mind a well-integrated understanding of multilingualism when considering the faculty of speech of a multilingual child; the child, however, should be regarded as an entireness and being investigated by one single method. In this case, all structures, rules of grammer and elements of each of the spoken languages should be compiled, including the specific conditions of socialization and living. These requirements concerning the diagnosis of the language still contain several unfulfilled conditions like the collecting of empiric results and the development of theoretical approaches concerning specific problems as to the “normal” and the “noticeable” linguistic development course resp. as well as the learning of the second language.