In this research a number of important and active phonological processes in standard German, spoken in Berlin, have been studied. In this regard, four dictionaries: Duden Universal W?rterbuch (1998), Langenscheidt (2002), Brock Haus (1996), and Panbeh-Chi (1379) have been used for gathering the data. Furthermore, two German informants had a four-hour interview to complete the data. In addition, books in the field of Phonology, whose names have been mentioned in the bibliography, have been used to determine the phonological rules. The most important phonetic-phonological processes in German are: aspiration of initial voiceless stops, devoicing of final voiced obstruents, assimilation of coronal nasals with the next oral consonant in the place of articulation and umlaut (change of the feature +back to –back in the case of back vowels). Among the mentioned processes, ‘aspiration of initial voiceless stops’ and ‘devoicing of final voiced obstruents’ have been shown to be more active than the others. Another important point about syllable structure in the German language is that the Sonority Sequency Principle (SSP) dominates the syllable structure in this language.