|Abstract:||This paper investigates the obstruent systems of Germanic and Romance varieties spoken in Northern Italy, specifically, the language islands of Mòcheno and Cimbrian, Tyrolean and the Italian dialects of Veneto and Trentino. The goal of the paper is (a) to explore the features of microvariation emerging between related varieties, (b) to determine whether (for the Germanic varieties) any typical features of language islands can be found, such as particularly conservative structures or (c) innovations unknown in other German dialects and, finally, to determine whether (d) language contact has left any traces in the structure of the languages involved. nWe find that microvariation between Germanic varieties occurs with respect to a phenomenon of intersonorant voicing of fricatives. Intersonorant voicing of fricatives occurs productively in the varieties of Mòcheno and Cimbrian (Lusern), but not in the Cimbrian varieties of Giazza and Roana, nor in Tyrolean. It can be interpreted as a conservative feature, maintained from earlier stages of the German Language. At the same time, the phenomenon has some innovative aspects, in that it involves all fricatives, differently from what happened in Middle High German. Microvariation is analyzed here in the framework of Optimality Theory and it is shown that the phenomenon can be modeled as minimal reranking between constraints, embedded in a core grammar common to all Germanic varieties. The comparison between the obstruent system of the Romance and Germanic varieties of the area shows that there is only one phenomenon which might be interpreted as the result of contact-induced change, the phenomenon of final devoicing of obstruents, which occurs both in the Germanic varieties and in Romance contact varieties of the Trentino. However, final devoicing can be interpreted as the result of selection of unmarked structures. Since unmarked structures may arise spontaneously in language change, final devoicing in Romance varieties is not necessarily a result of contact.