Originally developed in Scandinavia, national arthroplasty registers have spread worldwide during the last decade. The value of registers for quality improvement in arthroplasty has frequently been documented. However, for the development of a successful register a few key points should be taken into account. Uncontrolled loss of patients from the registry area should be avoided. Registers should form an integral part of a country's medical system. To realise the potential for improvement, it is crucial that physicians deal with the results in detail. Thus it is absolutely essential to involve the specialty societies in the interpretation and dissemination of results. With respect to revision rates, register data are usually more valid than meta-analyses of clinical studies. For every physician the most valuable data are those coming from a register in his own country; the development of national arthroplasty registers should therefore be continued.