An automated system is described that screens requests for laboratory investigations from GPs and delivers feedback with respect to the adequacy of the requests. The system has to replace and extend the current system in which feedback is provided on a manual basis each half year, based on the tests requested during a period of one month, randomly selected from the previous half year. It has been reported elsewhere that the manual system reduced the number of tests requested considerably. The criteria used by the automated system and the manual system are based on guidelines and work agreements that GPs have agreed to follow when requesting investigations. It is concluded that the automated system is very user-friendly and that in the order of 4–17% of the requested tests could be identified as unnecessary, with a false negative rate in between 4% (for hyperthyroidism) and 23% (for hypothyroidism). The achieved reduction in the number of tests is in addition to the reduction obtained in the manual system.