The epidemic of obesity is largely responsible for the high prevalence of metabolic syndrome in the developed world. Since 2001 with the development of the NCEP metabolic syndrome classification, simple pragmatic criteria have been available that can be applied in primary care across all continents to diagnose the syndrome. Although there is an ongoing debate about the level of thresholds that should be applied to individual features of the syndrome, it is likely that with further research a consensus will be reached in the near future. It is now clear that metabolic syndrome represents a condition of insulin resistance and ectopic fat accumulation associated with a proinflammatory and procoagulant phenotype. The syndrome is sometimes associated with other conditions such as non-alcoholic fatty liver disease (NAFLD), polycystic ovary syndrome, type 2 diabetes and cardiovascular disease. The purpose of this review is to discuss the clinical and laboratory diagnosis of the metabolic syndrome. The review discusses the various approaches to the investigation of people with the metabolic syndrome. Simple tools for clinical and laboratory diagnosis of metabolic syndrome are described. Some of the more complex biochemical tests that are now being applied in research to the diagnosis of associated conditions, such as NAFLD, are also described.