Learning about mathematics begins in the early years. Through their everyday activities, young children build important foundational knowledge and understanding of mathematics, especially when adults provide specific opportunities to learn and practice concepts and skills. Young children develop early on an informal understanding of important mathematical concepts about quantity, logical relationships, number operations, shapes, and space. Children can, however, acquire much deeper and more explicit knowledge if they are provided with high-quality mathematics education during preschool that will prepare them for more formal mathematics instruction in the later grades. Quality instruction in early mathematics is particularly critical for children with disabilities, such as cognitive delays, attention problems, and listening comprehension difficulties, as well as for those who are at high risk for later problems in school. In response to the Good Start Grow Smart federal initiative launched in 2002, states have developed early learning guidelines that include standards and outcomes for literacy, language, and mathematics for children ages 3 to 5 years. Early childhood and early childhood special education (EC/ECSE) publications have focused much attention on early literacy and language in the past few years. Teachers have, however, received less information on early mathematics. In this article, the authors describe current information on the development of early mathematical knowledge and offer suggestions for how EC/ECSE teachers can support mathematical learning in preschool children. (Contains 4 tables.)