A sense of number is now generally recognised as a central factor in learning, and later applying, mathematics. Consequently, number sense is increasingly emphasised in curriculum documentation related to mathematics. The Primary School Curriculum: Mathematics, published by the Government of Ireland in 1999, is no exception. It implicitly stresses the importance of number sense and draws teachers' attention to a range of key aspects. This article examines how numbers sense is defined generally, how it is explicated in the curriculum for the youngest children at primary school, and the nature of the guidance that curriculum documentation provides to teachers in relation to developing young children's number sense. The curriculum documentation is examined in terms of a socio-culturally related framework which the author developed for considering number sense as it pertains to young children. This framework has four aspects: pleasure and interest in number; understandings of the purposes of number; quantitative thinking; and awareness/understanding of numerals. A number of areas of omission were identified in the teacher guidelines that accompany the curriculum documents. Implications are drawn with respect to a review of the current documents related to early years mathematics, and areas for potential development are outlined.