Objective: To assess the effect of Daflon 500 mg on upper lymphoedema occurring after conventional treatment of breast cancer. Design: Open, pilot, single centre trial. Setting: Hospital outpatients attending a University Hospital. Patients: Ten female patients (aged 44–64 years) whose previous treatment for breast cancer was followed by upper limb lymphoedema (mean (SD) time delay = 17±7 months). Interventions: Oral administration of a daily dose of two tablets of Daflon 500 mg for 6 months. Main outcome measures: Symptoms, affected upper limb volume and parameters of radionuclide lymphoscintigraphy using technetium-99m. Results: All patients experienced improvement of symptoms and limb volume (mean volume decrease of the swollen limb: 6.80%). Functional parameters assessed with scintigraphy were significantly improved (half-life: 147.4 (14.9) to 144.1 (14.9) min, p < 0.01; clearance of the colloid: 25.9 (2.5) to 28.3 (2.8) <l/min, p < 0.05; lymphatic speed of the colloid: 7.7 (0.3) to 8.0 (0.2) cm/min, p < 0.05). Conclusion: These preliminary results suggest that this therapy is effective for the treatment of lymphoedema.