"Number sense" is "an intuition about numbers that is drawn from all varied meanings of number" (NCTM, 1989, p. 39). Students with number sense understand that numbers are representative of objects, magnitudes, relationships, and other attributes; that numbers can be operated on, compared, and used for communication. It is fundamental knowledge that mathematics, grounded in numbers and with all its rules and operations, has an inherent "sense" that can be used by the student in flexible ways to solve problems. Number sense continues to be developed throughout a student's mathematics education and applies to a wide range of concepts. Number sense is not a curriculum topic but, rather, is the connectedness of number knowledge throughout the curriculum. This article offers strategies for promoting number sense development across the grade levels: early number sense structures, numerical understanding, and the development of more complex numbers and number relationships. (Contains 3 figures.)