This paper attempts to develop a comprehensive model for the problem of internal vs. external conjunction (Halliday & Hasan 1976). It is first argued that the distinction between internal and external conjunction is not merely a matter of semantics, but that the two types are semiotically significant categories. By postulating that internal and external conjunction are cryptotypically anchored in the speaker-encoding vs. content-related grammar of their main clause, it can be explained why and how syntactic criteria like clefting or nominalization 'react' to the semantic distinction between the two types of conjunction. Secondly, it is argued that the internal category should be subdivided into two grammatically distinct types of conjunction, which are related to the modal and the speech functional grammar of their main clause. Finally, this analysis is used to propose a better delineation of the modal and the speech functional subtypes of the internal category.