This dissertation is a report on the articulatory and acoustic investigation of Seneca speech as compiled by a native speaker of the Seneca language. The body of the dissertation consists of four chapters. In Chapter 1, earlier analyses of the sound patterns of Seneca are introduced and discussed. Several problematic aspects of Seneca are highlighted and these are discussed in later chapters. Chapter 2 is a subjective analysis of Seneca articulation. The author has discovered that the Seneca language is articulated from a different articulatory base (referred to as the "Seneca neutral position"), than is found in other languages. Of special interest are the vowel combinations as well as the sequences of consonants in syllable initial position such as /kn/ and /kd/ which are produced with a unique order of articulatory gestures. Chapter 3 displays the results of an acoustic study of Seneca speech. The primary instruments employed in this study were a sound spectrograph and a pair of pneumotachometers which were coupled to a specially modified surgical mask so that the air flow in the nasal and oral cavities could be measured independently. Many of the proposals made in the subjective analysis are substantiated by the results of the instrumental analysis. Chapter 4 presents a discussion of the theoretical consequences of this study. In particular, the facts of Seneca articulation suggest the inapplicability of the Chomsky & Halle distinctive features as presented in the book The Sound Pattern of English (1968). The author proposes supplementing the tongue body features high, low, and back with two additional features which specify a degree of mouth opening due to the tongue blade/mandible position. These additional features, [± open], [± close] are necessary to account for the articulation of Seneca.