Policymakers like to make use of age criteria, because they provide a transparent and seemingly objective standard. In reality, however, age limits are not as innocent as they appear: distinctions on the basis of age are often irrelevant and the actual age thresholds tend to be arbitrary. Age limits can also be criticised from a theoretical perspective: how can the heterogeneity of today's older people be reconciled with uniform age-defined classes? In response to a European Union Directive of 2000, Belgium implemented strict anti-discrimination legislation. This provides all the more reason to ascertain the prevalence and justification of the use of age criteria in legislation. Belgium is a federal state with three communities and three regions, and the scrutiny has been restricted to the Flemish community and region. All legislation has been screened for the use of 50 or more years as an age criterion, and all occurrences have been critically examined. The paper focuses on three fields of statutory regulation: early retirement, concessionary public transport fares, and the different care entitlements of people with disabilities and of older people. Evidence of age discrimination was found, although often in a form that benefits older people. The justification of the age criterion was often inadequate, so the adoption often appears no more than convenient standard practice. The paper concludes that policy makers should consider the systematic replacement of age thresholds by other criteria.