Congenital venous malformations (VMs) are the most common vascular abnormalities. Their treatment can be complex, depending on their size and surrounding tissues involvement. To date, sclerotherapy is considered the gold standard for the treatment of VMs. This technique, which aims to destroy the endothelium and thus cause fibrosis and retraction of the vascular lesion, is less effective in voluminous VMs. Endovenous thermal ablation is a widely validated treatment in the management of venous insufficiency, showing better efficacy than sclerotherapy in terms of trans-parietal vessel destruction. This approach has therefore also been described in the treatment of VMs. This technique has been introduced for the treatment of complex VMs at the Centre for Malformations and Rare Vascular Diseases of the CHUV.