This article discusses structural factors responsible for a number of subtle differences in the outcome of language contact in Brussels (Belgium) and Strasbourg (France), and suggest that sociolinguistic factors have little explanatory power in this area. Differences between the rules for past participle formation in Dutch as spoken in Brussels and Alsatian as spoken in Strasbourg are claimed to be responsible for the differences in the integration patterns of French past participles that maintain French morphology, the so-called unintegrated French past participles. The latter occur only in French-Alsatian contact but not in French-Dutch contact. Thus, this article offers counterevidence to Thomason and Kaufman's (1998) claim that the sociolinguistic history of speakers and not the structure of their language is the primary determinant of the linguistic outcome of language contact. Evidence from other bilingual communities along the Romance-Germanic frontier provides additional support in favor of the hypothesis that structural rather than sociolinguistic factors are responsible for the contact patterns observed along the frontier. (Contains 22 references and 2 tables.) (Author/VWL)