Frequencies and discourse functions of grammatical subject types were investigated in a corpus of forty results and discussion sections selected from four disciplines (Applied Linguistics, Psychology, Chemistry, and Environmental Engineering). The results and discussion sections were selected from research articles that were published in 2008-2012 issues of prestigious high journals of the four disciplines. The results and discussion sections were analyzed for realizations and discourse functions of grammatical subject types adopting the taxonomy suggested by Ebrahimi (2014). The results suggested that the selections, frequencies and discourse functions of grammatical subject types were highly imposed by the macro functions of the results and discussion sections and the conventional rules of writing in the disciplines. One immediate implication for the outcome of this study is that writers and instructors need to keep in mind that they must be fully aware (and follow suit) of how the implementation of grammatical subjects are imposed and restricted by disciplinary conventions.
