Noting that assumptions about the teaching and learning of early childhood mathematics have changed substantially since the 1970s, this chapter examines recent research that may inform curriculum development in early childhood mathematics. The chapter begins with a consideration of the theoretical perspectives for defining an appropriate mathematics curriculum, focusing on mathematics as a dynamic discipline, the construction of knowledge, perceiving relationships between or within mathematical ideas, and the role of social interaction in learning mathematics. The chapter then interprets research on children's mathematical thinking, including the development of number sense, the concept of quantity, part-whole constructions, counting and numeration, place-value instruction, problem-solving abilities, representation, geometric concepts, and spatial sense. Finally, the chapter reviews instructional issues that must be addressed when creating learning environments, drawing from current research that considers classroom discourse, teacher questioning, and instructional decision making. (Contains approximately 90 references.) (KB)