Since the National Certification Board for Diabetes Educators (the organization responsible for certification of diabetes educators in the USA) was established in 1986, the importance and prevalence of professional certification have increased dramatically. New certification programmes are increasingly being developed for more and more occupations and professional specialties, while existing certification organizations are expanding their certification offerings. The authors explain terminology and discuss a number of issues around certification, and describe key points for consideration by those planning to establish a certification programme.