About 0.4 million people (0.6% of the UK population) are on warfarin and the average interval between blood tests is 3 weeks.  Communicating INR results, anticoagulant (AC) dose and clinic appointments to these patients presents a major logistical challenge.  The post is the traditional channel of communicaion but it is costly, slow and unreliable.  An automated voicemail system, INR RELAY (pacehealthsystems.com), was developed and implemented at Basildon Hospital in 2000.  We required a system which could help a large number of laboratories to deliver large amounts of computed data rapidly (in sufficient time to influence the same day's dosage) and safely to a vulnerable patient population (elderly, often techno phobic) in an acceptable way.  We opted for AUTOMATIC TELEPHONE DIAL-OUT as the communication channel of choice for patients.  We opted for FILE TRASFER BY MODEM as the communication channel of choice for laboratories.