As English becomes an international language in the world, there is a growing interest in developing English skills from early childhood. In Korea, the demand for English as a foreign language education for young children has increased considerably in the past decade. However, little is still known about the professional knowledge of an early childhood (EC) language teacher (Borg, 2006a; Nunan, 2010; Pinter, 2011). The main purpose of this study is to develop and validate a survey of Early Childhood English Teacher Knowledge (ECETK), an instrument designed to identify the domains of teacher knowledge. To accomplish its goal, this study poses the following three research questions: (1) based on the review of the literature on Second/Foreign (L2/FL) education, Early Childhood (EC) education and Early Childhood (EC) language education, what are the components of EC English teacher knowledge? (2) Do these components correspond to the factor constructs that underlie Early Childhood English Teacher Knowledge?, and (3) What is the reliability of the identified factors in this instrument when used with EC Korean teachers of English? The initial version of the ECETK was developed based on a theoretical model of teacher knowledge proposed by Shulman (1987) and later re-conceptualized by Grossman (1990), and an in-depth literature review. This version of the instrument was piloted on 40 Korean teachers of English. Based on validity (construct, content, and face) and reliability (Cronbach-alpha, Split-half) analyses of this study, the instrument was revised. The content validity of the revised survey was examined by a panel of three experts whose suggestions were used to further improve the instrument. The final version of the survey was administered to 336 EC English teachers in Korea. Exploratory factor analysis was used to identify the structure of the ECETK items in order to establish its construct validity. The six-factor solution yielded the following factor constructs: Pedagogical Knowledge and Teacher Language Awareness, First Language Acquisition, Linguistic Knowledge, Knowledge of Context, Language Play, and Second Language Acquisition. The reliability analysis of the identified factors provided high internal consistencies as computed by Cronbach's alpha that range from 0.78 to 0.92 with a total coefficient alpha equal to 0.94. The results of this study indicate that the domain of subject matter knowledge is multidimensional and not unitary as earlier theoretical models of teacher knowledge have suggested (Shulman, 1987: Grossman, 1990). In addition, it was found that Language Play and Teacher Language Awareness may not belong to the same category as it has been proposed in the literature, but instead cross along the pedagogical content knowledge and general pedagogical knowledge dimensions. Theoretical and practical implications of these findings and suggestions for further research will be discussed. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]