||In the vast majority of northwestern Chinese dialects (NWDs) spoken in Shanxi 山西, Shaanxi 陕西, Qinghai 青海, Ningxia 宁夏, Gansu 甘肃, Xinjiang 新疆, and Inner Mongolia 内蒙古, the aspect marker -ZHE 着 has a number of peculiar characteristics. The most prominent one is that it takes a special position where no verb suffix is expected to occur, i.e., it is placed after the object (“V+O+-ZHE”) rather than immediately following the verb (“V+ -ZHE+O”) as in Standard Mandarin and other varieties of Chinese. Furthermore, -ZHE can co-occur with much more types of verb constellations in NWDs than in other Chinese dialects, including stative verbs (e.g., shi 是 ‘copula’, you 有 ‘have’, zhidao 知道 ‘know’) and achievement verbs (e.g., si 死 ‘die’, ying 赢 ‘win’, lai 来 ‘come’). In addition, the component verbs in verb-chaining constructions, such as serial verb constructions, are often found accompanied by -ZHE in the dialects spoken in Shaanxi, Gansu and Xinjiang, even when the verb does not signal an ongoing action or a state of being. This thesis argues that the peculiarity found in NWDs is a result of syntactic change induced by the contact with the non-Han languages spoken in Northwest China, including Mongolian, Turkic and Tibetan languages. The contact-induced change presents an interesting case illuminating the very nature of language as a self-organizing and adaptive system. The “V+O+-ZHE” configuration reflects a perfect compromise between the two types of languages in contact: in such a configuration, the canonical VO order of Chinese is maintained, while by moving the verb suffix to the clause-final position, it also complies with the verb-final trait of the Altaic languages.