In rheumatoid arthritis nowadays a more aggressive treatment strategy is followed based on early consistent use of second-line agents frequently given in combination. This approach requires an accurate monitoring of the disease activity to follow the course of the disease and to evaluate therapeutic interventions. International consensus is reached over a core set of disease activity variables, including: a 28-joint count for tenderness and swelling, an acute phase reactant, patient's pain and global disease activity, physician's global disease activity, functional disability and radiographs. Guidelines for measurement techniques need to be further specified. Indices of disease activity are developed to improve the unambiguous interpretation of disease activity and comparability of trial results. These measures can be divided in measures for current disease activity and improvement criteria. Further validation will be necessary to adapt finally a uniform measurement technique. The usefulness of self-administered joint counts needs to be studied further.