L1 attrition is increasingly being studied as a feature of bilingualism, taking into account the parallel process of L2 language acquisition in a migrant situation. Such situations may foster L1 attrition as a result of insufficient L1 input and competition or interaction with the language of the host community. In a study of 27 German late bilinguals resident in Ireland, the question of a possible interaction between the two language systems (German and English) is addressed. This paper reports on the results of two of the elicitation instruments used - a C-test as a measure of global language proficiency, and a verbal fluency task as a measure of lexical retrieval and bilingual dominance. The former is an unspeeded integrative task, while the latter taps lexical access as a function of the relative activation levels of the languages. The analysis focuses on the proficiency profiles of the bilingual participants vis-à-vis a German and an Irish control group to establish the level of L1 attrition and L2 acquisition, and the degree with which L1 and L2 proficiency correlate.