Computerised decision support software (CDSS) for anticoagulation management has become established practice in the UK, offering significant advantages for patients and clinicians over traditional methods of dose calculation. The New GMS Contract has been partly responsible for this shift of management from secondary to primary care, in which INRstar has been the market leader for many years. In September 2004, INRstar received the John Perry Prize, awarded by the PHCSG for excellence and innovation in medical applications of information technology.