We have developed a telemedicine system for blood transfusion work, to supply the local hospital laboratory with an expert opinion from the central reference laboratory. The telemedicine system allows remote inspection and interpretation of pre-transfusion tests, which are performed by ID-cards (micro-tube gel technology). The system was installed at three blood transfusion laboratories in Slovenia, approximately 70 km apart. Validation of the telemedicine system was performed using 99 clinical cases selected randomly from routine work. Two groups of immunohaematology specialists participated. Group A (n = 8) performed the read-out of the pre-transfusion tests on ID-cards by using the telemedicine system. Group B (n = 2) then read the ID-cards independently using the standard visual method. All 98 final interpretations which were recorded using the telemedicine system were correct. We recorded 591 micro-tube read-outs of agglutination strength using the telemedicine system, of which 582 were correct. For comparison, we recorded 591 micro-tube read-outs using the standard visual method, of which 582 were correct. The validation proved that the telemedicine system was suitable for operational use.