Summary. Four questionnaire surveys were conducted over a penod of 20 years to evaluate long-term effects of haemophilia treatment in the Netherlands. The response to the prestructured questionnaires in 1972, 1978, 1985 and 1992 vaned between 70% and 84%. Data concerned treatment modahties, bleeding episodes, hospitahzation, absenteeism, jomt impairment and employment. Results over the penod 1972-92 for patients with severe and moderately severe haemophilia showed that the use of prophylaxis had sharply increased (from 21% to 45%), äs was the case for home treatment (from 4% to 62%) Consequently, the annual mean number of bleeds dimimshed from 19 to 13. Absence from school was markedly reduced (from 32 to 5 days), and sick leave in employed patients had also dimimshed (from 26 to 22 days). Furthermore, the use of mpatient hospital facihties, äs well äs employment in haemophilia patients, had nearly equalled that of the general Dutch male population. The self-reported degree of jomt impairment showed no overall improvement, but in patients aged under 35 years there seemed to be a shght reduction in severe impairment. Patients aged under 15 years finally had no severe impairment at all. Social parncipation can only be further improved if arthropathy is prevented from an early age. Therefore adequate prophylactic regimens and close monitonng of )omt impairment in young adults are needed.