Rheumatoid arthritis (RA) is diagnosed based on phenotypic characteristics. The 2010 ACR/EULAR criteria were derived with the aim of classifying RA earlier in the disease course than the 1987 ACR criteria. When reviewing thus far published validation studies, it is clear that the 2010 criteria can be fulfilled earlier in time than the 1987 criteria. Therefore, the taskforce that derived the 2010 criteria has succeeded in their main objective. Furthermore, it has been repeatedly shown that the sensitivity of the 2010 criteria is increased compared with the 1987 criteria, but the specificity decreased. As classification criteria aim to arrive at homogeneous groups of patients in order to compare the results of clinical or experimental studies, this decrease in specificity is of concern, as patients with diagnoses other than RA can test positive on the criteria. With regard to diagnosing RA, the overall trend in the data is that early arthritis patients in the rheumatological setting who fulfil the 2010 criteria have a high probability of the disease. Not fulfilling the criteria, in contrast, does not rule out RA in these individuals.