In part I some observations are made about transitivity; part II (see Halliday (1967: 'Notes on transitivity and theme in English, part II')) deals with 'theme', which is used as a general term for all those choices involving the distribution of information in the clause; in part III (see Halliday (1968: 'Notes on transitivity and theme in English, part III')) transitivity is reconsidered in the light of what has been said about theme. The approach is 'systemic', i.e. the grammar takes the form of a series of 'system networks', in which each of those networks represents the choices associated with a given constituent type (e.g. clause, NP).