SummaryProphylaxis is the recommended treatment for children with severe haemophilia A, but whether prophylaxis should be continued in adulthood is still under debate. Previous studies with limited follow-up have suggested that some patients may be able to stop prophylaxis in adulthood, while maintaining good joint health. This single-centre observational cohort study examined patients with severe haemophilia A born 1970–1988 without inhibitor development, and assessed the long-term consequences of discontinuing prophylaxis. Patient-initiated changes in prophylaxis, including all switches to on-demand treatment lasting a minimum of two consecutive weeks, were recorded from the time self-infusion began until the last evaluation. Sixty-six patients were evaluated at a median age of 32.4 years: 26 of patients had stopped prophylaxis for a median of 10 years, 15 had interrupted prophylaxis and 59 had continued prophylaxis. Annual joint bleeding rate (AJBR), Haemophilia Joint Health Score (HJHS-2.1; 0–124 points), radiological Pettersson score (0–78 points) and Haemophilia Activities List score (HAL; 100–0 points) were compared between patients who stopped and patients who continued prophylaxis. Although self-reported bleeding rates and functional limitations were similar in both groups (AJBR: 1.5 vs 1.2 and HAL: 84 vs 84 for those who stopped and continued prophylaxis, respectively), objective assessment of joint status showed increased arthropathy after 10 years of on-demand treatment in patients who stopped prophylaxis compared with those who continued (HJHS: 23 vs. 14 and Pettersson: 16 vs 5, respectively; P< 0.01). These results support continuation of long-term prophylaxis in adults and demonstrate the need for objective monitoring of joint status.Trial registration: Dutch Trial Registry number 3098; UTN U1111–1121–7069.