A recurring question in the study of the specialized English used in various technical disciplines is the degree to which contextual variables--including subject matter--account for the particular distributions of lexicogrammatical features in texts of different disciplines. Two contextual variables related to role relationships in the semiotic structure of the situation are the specialization of the intended audience and the global text function or authorial purpose. One way to compare the impact of each of these variables on text structure is to examine the distributions of the lexicogrammatical features which realize the interpersonal component, e.g., person, disjunct adverbials, clause mood and modality, in texts where both of these variables have different values while all other contextual variables remain constant. Such was done with 16 written, monologic texts in recombinant DNA research. Within each text, a sample was taken of approximately 1,000 words and counted according to the lexicogrammatical features realizing the interpersonal component. An analysis of the findings reveals a lower degree of audience specialization correlates with a greater degree of interactiveness. Moreover, the lexicogrammatical features which realize the interactiveness tend to be distributed according to global text function; texts whose aims are to persuade or instruct their readers tend to be more interactive than texts which aim merely to narrate or inform. Overall, global text function appears to be a primary variable determining the distribution of the lexicogrammatical features of interactiveness, while specialization level of the intended audience appears to be a secondary variable. (HOD)