abstract: This study explores the development of negation and the Negation Phrase (NegP) in bilingual children learning both English and Spanish. I analyze the speech of four children growing up in the United States who are learning English and Spanish simultaneously in order to establish steps of parameter setting for negation. The transcripts have been taken from Pérez-Bazán’s bilingual corpus from CHILDES (Child Language Data Exchange System). The thorough analysis of the selected corpus data gathered from children ages 2;0 and 3;3 determines the steps children follow in order to develop mastery of negation and the NegP. This study is an addition to the body of research surrounding language acquisition and the concept of Universal Grammar’s Principles and Parameters framework. The bases for this study is Klima & Bellugi’s (1968) established three steps for acquisition of negation by children in English, as well as Zeijlstra’s (2004) analysis of languages in regards to phases of the Jespersen cycle. The data of this study suggest that there are five basic steps to parameter setting, and that as utterances become syntactically more complex, children value uninterpretable features with interpretable ones. This is seen in both languages studied. The parameters categorized based on the data available for this study are the following: 1) negative particle outside of the VP, 2) NegP creation and development with preverbal negative marker, 3) Negative Concord (NC), 4) True Imperatives (banned or not), and 5) Negative Polarity Items (NPI). Also important is the placement of the NegP, as it is above the TP in Spanish and c-commanded by the TP in English. The development of the NegP and uninterpretable negation [uNeg] valuation by interpretable negation [iNeg] is also explored in the utterances of the four children studied. This study confirms Klima & Bellugi’s account of steps and further defines child negation in English as well as in Spanish. The focus on [iNeg] and [uNeg] features is further explained using Zeijlstra’s Phases of the Jespersen cycle as a springboard. I add salient information regarding parameter setting and how negation and the NegP are developed across two languages. / Dissertation/Thesis / Doctoral Dissertation English 2015