The literature on the mixing of two languages in children bilingual from birth distinguishes code switching on different levels, switching within the same sentence or utterance (‘intra-sentential switching’, ‘intra-utterance switching’ following Genesee, Boivin & Nicoladis, 1996 : 428–429) and mixing between sentences or utterances in the same conversation (‘inter-sentential switching’, ‘inter-utterance switching’). This article presents a longitudinal study on inter-sentential switching, still rarely investigated, in four bilingual French-German children between the age of two and four years. The main goal is to detect the characteristics of such switching, to increase our understanding as to whether they are comparable to intra-sentential switching in terms of frequency and motivation. Inter-sentential switching is much more frequent than intra-sentential switching. Analysis of the data shows that inter-sentential switching is frequent in the weaker language of children classified as imbalanced bilinguals during the study. In contrast, inter-sentential switching is nearly absent in children who are balanced bilinguals. Results also show that inter-sentential switching does not generally follow the characteristics of code-switching, but rather depends on emotional and cognitive factors.