A growing body of research is emerging that investigates the teacher knowledge base essential for supporting reading and writing development at the elementary school level. However, even though increasing recognition is given to the pivotal role that preschool teachers play in cultivating children's early literacy development, considerably fewer studies have examined the knowledge base of these early childhood educators. This paper will discuss the existing research literature and then examine a recent study that investigated the knowledge constructs of 20 preschool teachers. Findings indicate that preschool teachers lack the disciplinary knowledge required to promote early literacy and, in fact, tend to overestimate what they know, creating a potential obstacle for seeking additional knowledge. Recommendations for strengthening professional development programs and developing more robust measures of preschool teacher knowledge are proposed.