This study is concerned with the lemmatic structure, thematic agenda and normative and non-normative aspects of the Mekhilta de-Rabbi Ishmael, with a view to establishing the level of coherence therein. The Mekhilta is one of the oldest exegetical Midrashim dated at the earliest circa 3rd/4th C.E. It is a Midrash which covers 29% of the book of Exodus and although commonly referred to as a 'Midrash Halakhah' (normative Midrash), less than half of its text is concerned with norms. Based on a fresh investigation of the entire text of the Mekhilta as presented in the Lauterbach edition, while taking into account manuscripts and early prints, I describe all the structural arrangements both external and internal, working downwards from the largest divisons - the titled tractates - through the smaller lemma-comment units (= biblical quotation + rabbinic comment) concluding with the smallest - 'lemma-gloss components' (= biblical quotation + immediate initial comment) which mark out the Mekhilta's macrostructure. Within the lemma-comment units, I isolate other structural components such as the contiguous-units (=all quotations of or from one verse + commentary on all those quotations), and I identify microstructual elements such as proof quotations (= biblical quotations cited in proof of rabbinic commentary), repeated and requoted lemmata (= biblical quotations repeated for further comment) and formulaic language (= Rabbi x says introducing rabbinic statement, talmud lomar introducing biblical quotations). I also describe the 'Stam' structure in the Mekhilta and discuss the 'Stam' concept in rabbinic literature in general (chapter 1). Turning to the Mekhilta's content, I raise the problems of categorising its themes. I distinguish themes that are exclusive to one tractate from those that are collective, that is, are scattered within a tractate or over a number of tractates (chapter 2). In an attempt to reconstruct the conventional distinction of halakhic and aggadic content, I suggest a definition of normative and non-normative material and describe various forms of these. I present tables displaying the quantities of normative and non-normative material both within the book of Exodus and within the Mekhilta. I illustrate the relevance of the analysis of literary phenomena for understanding the potential unity of the Mekhilta by examining the treatment of the theme of idolatry throughout the tractates (chapter 3).Examining the possible meanings of 'coherence' in texts, I come to the conclusion that, when the interplay of lemmatic and thematic aspects is taken into account, the Mekhilta can be justifiably considered a 'coherent' text.