In 1991 the public hospitals in Paris set up a plan to regulate the prescription of IVIg. The plan includes an expert committee and reliable data collection. The expert committee has a threefold mission: i) perform an annual up-date of IVIg classification using three categories: accepted indications (group I), currently deabated indications (group II), and unwarranted indications (group III); ii) develop guidelines for improved therapeutic strategies; iii) stimulate research. Data on use of IVIg are collected in 16 pilot hospitals. These data designate IVIg prescriptions by indication. Data are centralized by the CEDIT which publishes an annual report. Between 1988 and 1991, prescription of IVIg increased at an average annual rate of 33%. Between 1991 and 1996, the amount of IVIg used leveled off: approximately 330 kilograms/year, excluding research protocols. In 1997 there was a decline to 299 kilograms accounting for a total expenditure of 44 million French francs (US$ 6.7M). In 1997, group I prescriptions represented 80% of all IVIg prescriptions, group II 9.8% and group III 9.1%. Comparison of medical practice with a scientificaly recognised reference made it possible for AP-HP to set up an effective regulation of IVIg prescriptions. The longevity of this evaluation work is by itself a success.