Objectives: Cyclophosphamide is used in high dose in the conditioning regimen of allogeneic and autologous stem cell transplantation and early post-transplant as prophylaxis of graft-versus-host disease (GVHD). The risk of bladder toxicity and hemorrhagic cystitis is well established. However, preventive measures differ depending on local protocol.Methods: We conducted a survey among Belgian transplant centres to identify differences in preventive measures after high dose cyclophosphamide. All 15 JACIE accredited Belgian transplant centres were asked to complete a short questionnaire. Centres who did not use high dose cyclophosphamide (n=2) were excluded from analysis.Results: All 13 centres were included. High dose cyclophosphamide was used in conditioning regimens pre-allogeneic stem cell transplantation in 11 centres (84,6%), pre-autologous stem cell transplantation in 5 centres (38,5%) and GVHD prophylaxis in 11 centres (84,6%). Preventive measures included hyperhydration and forced diuresis, administration of mesna and insertion of a bladder catheter. Hyperhydration and mesna were reported in all centres (100%), however the dosing of mesna varied between centres. Three centres (23,1%) reported insertion of a bladder catheter as a standard precaution in all patients. Motivation included either historical reasons or previous cases of severe hemorrhagic cystitis. In three centres (23,1%) a standard interval for diuresis was defined (waking patients up at night). In most centres (92,3%) urine output was monitored with a specific target urine output defined in 4 centres (30,8%).Conclusion: This survey identified several differences in preventive measures after high dose cyclophosphamide among Belgian transplant centres. An interesting difference is the preventive use of a bladder catheter, often causing discomfort to patients. As this is not a standard procedure in most centres, this study can serve as a benchmark to question its systematic use. In general, more evidence is needed to identify best practice and ...