We conducted a questionnaire survey of haemophilia treaters participating in the Fourth Seminar on Regular Replacement Therapy (sponsored by Baxter Bioscience, 4 March 2006) to clarify the current status (up to January 2006) of replacement therapy for haemophilia. The haemophilia treaters including medical doctor, nurse belonged to 48 institutions located in the 23 prefectures of Japan. Topics included age at the initiation of regular replacement therapy (prophylaxis), and expected future situation of patients who are currently receiving prophylaxis. Data were collected from 1267 patients with haemophilia A and 273 patients with haemophilia B who had been treated at the represented institutions. Of these haemophilia A and B patients, 23% and 16% had received a prophylactic treatment regimen respectively. A breakdown of each disease by severity demonstrated that of the patients with severe haemophilia A and B patients, 27% and 18% of patients received a prophylaxis treatment, compared to 17% and 19% of patients with moderate type, and 1% and 3% of patients with mild type respectively. Of those severe haemophilia A and B patients receiving prophylaxis, the percentage of primary prophylaxis, which means prophylaxis begins under 2 years of age, was still small for 24% and 29% respectively. However, approximately half of the patients received prophylaxis during the age of 2-14 years, which suggests that secondary prophylaxis is widely spread in the age group in Japan. Problems in introduction of prophylaxis include difficulty in peripheral venous access, a lack of understanding of the therapy by the caregiver. In addition, the fear of inhibitor development, as well as the psychological anxiety in paediatric patients, was also mentioned as barriers to initiating and continuing prophylaxis.