In this paper, we report on a qualitative analysis of co-occurring discourse markers, that is, sequences of adjacent discourse markers that belong to the same unit but may express different functions. We examine several formal and functional features of these co-occurring strings on the basis of corpus examples extracted from conversational data in English. In particular, we focus on scope, meaning-in-context (or functions), syntactic category and position. Our analysis reveals several degrees of integration: differences in scope allow us to differentiate juxtaposition and combination of markers. In the case of combination, difference in meaning integration allows us to distinguish addition from composition of markers. We pay particular attention to in-between and ambiguous cases such as and so or and then, which instantiate different degrees in our cline of co-occurrence depending on the meaning that can be interpreted from the cluster. We finally discuss the implications of such fine-grained distinctions from the perspective of systematic corpus annotation.