Recent proposals for the revision of diagnostic criteria for gestational diabetes mellitus (GDM) have engendered worldwide debate. Within and between countries there is disagreement between obstetric, medical and endocrine groups regarding the diagnosis and management of GDM. There have been many articles written recently on this topic in an attempt to clarify opinions and, in some cases, promote a more unified approach. This review aims to discuss the criteria currently in use for the diagnosis of GDM and proposes the universal acceptance of the International Association for Diabetes in Pregnancy Study Group (IADPSG) GDM diagnostic criteria. It also aims to put into perspective the importance of GDM and its increasing prevalence, irrespective of the criteria used for diagnosis. Other factors associated with GDM diagnosis are also covered, including the epidemiology of testing for GDM around the world, the suggested elimination of a two-step diagnostic approach, the cost-effectiveness of testing and the approach to testing in resource-poor settings.There is a continuous relationship between glycemia and adverse pregnancy outcomes.Identifying gestational diabetes mellitus (GDM) provides an opportunity for meaningful health interventions to prevent Type 2 diabetes mellitus and other associated morbidities later in life.Unified criteria will facilitate research into the area of GDM treatment and outcomes.The increased GDM prevalence with new GDM criteria is concordant with the increased prevalence of impaired glucose tolerance in the general population.Testing for GDM is cost effective.The option of using fasting blood glucose alone for GDM diagnosis requires further investigation in different populations/ethnic groups.In resource-poor settings, the use of simplified protocols for testing, including the use of finger-stick glucose measurements, is an area of ongoing investigation.The use of the glucose challenge test and a two-step diagnostic process is not recommended.