Data were obtained from the National Child Development Study (NCDS), a large-scale longitudinal study in the United Kingdom following up a sample of people born in a single week in 1958 through to adult life, to demonstrate that poor numeracy skills have a major impact. At age 37, a 10 percent sample of 1,714 cohort members were interviewed and tested for functional literacy and numeracy skills. The assessments were composed of tasks that cohort members were likely to come across in their everyday lives: eight literacy and nine numeracy tasks, each with two or three subquestions. Analysis was designed to see to what extent numeracy problems were subsumed under literacy problems or constituted a significant problem in their own right. Cohort members were placed in four categories: poor numeracy and literacy; poor numeracy and competent literacy; competent numeracy and poor literacy; and competent numeracy and literacy. Seventy percent were competent in both. Evidence showed people without numeracy skills left school early, frequently without qualifications, and had more difficulty getting and maintaining full-time employment. The jobs entered were generally low grade with limited training opportunities and poor pay and prospects. Women with numeracy difficulties appeared especially vulnerable to exclusion from the clerical and sales jobs to which they aspired. Teachers had very limited success in identifying incipient numeracy problems. Women tended to have less competence in certain kinds of numeracy. (The numeracy tasks used in the assessments are appended.) (YLB)