OBJECTIVES: Fludarabine (F) is a mainstay treatment for CLL. Despite the availability of an oral formulation with equivalent efficacy and improved patient acceptability, many centres use an IV generic formulation assuming it is cheaper. A cost-minimisation analysis was undertaken on the two formulations. METHODS: The model assessed oral vs IV F and combination with oral/IV cyclophosphamide (FC). It included: European acquisition values defaulted to generic prices; body surface area 1.75m2; mg/m2 dosages oral F 40, IV F 25, oral C 150, IV C 250; dosage days/cycle F 5 / FC 3 for 6 cycles/patient. Published adverse events rates were equivalent except for IV administration complications (8% default) and diarrhoea (oral F 34.6% vs IV F 11.3% -Grade 1/2 and 3.8% vs 0% - Grade 3/4) - 2% managed in hospital. Equipment and clinical resource costs were defaulted to published rates and authors’ centres. A sensitivity analysis assessing minimum and maximum potential costs was applied.   RESULTS: Acquisition costs per treatment course were higher for oral vs IV (F - €5,334 vs €1,313 FC - €3,213.16 vs €894). However IV costs increased with adverse events (oral vs IV complications mean €0 vs €40, diarrhoea €1 vs €0) and hospital resource costs (oral vs IV F - €18 vs €4,200, FC- €18 vs €2,520). Direct oral vs IV treatment costs per patient were F - €5,353 vs €5,553 (range €5,334-€5,353 and €5,513-€5,577), FC - €3,232 vs €3,454 (range €3,214-€3,233 and €3,414-€3,478). Modelling oral adoption in 100 patients - 80% IV F / 20% IV FC, a 100% and 90% switch respectively resulted in €19,943 mean cost savings, releasing funding and resources for improved care and patient throughput. CONCLUSIONS: Oral fludarabine acquisition costs are higher than generic IV, but cost-minimisation modelling demonstrated reduced direct costs with oral fludarabine, while also being preferred by patients.