Successful treatment of vascular anomalies has eluded the physician until now, despite various treatments utilised. Bleomycin has been successfully used in intralesional injection treatment of cystic hygromas and haemangiomas, based specifically on a high sclerosing effect on vascular endothelium. In a prospective study of 95 patients, the effectiveness of intralesional bleomycin injection (IBI) treatment in haemangiomas and vascular malformations was evaluated and documented. Complete resolution or significant improvement occurred in 80% of all patients treated. Complete resolution occurred in 49% of haemangiomas, 32% of venous malformations, and 80% of cystic hygromas. Significant improvement occurred in 38% of haemangiomas, 52% of venous malformations, 13% of cystic hygromas and 50% of lymphatic malformations. Of the six patients who presented with a painful lesion, four experienced complete resolution and two had significant improvement to treatment. Local complications encountered were superficial ulceration occurring in 2 patients, and cellulitis in 1 of the 95 patients. Systemic complications were flu-like symptoms in three patients and partial, transient hair loss in two patients. None of the patients presented with haematological toxic effects or signs of pulmonary involvement (fibrosis, hypertension). IBI is an effective treatment in haemangiomas and vascular malformation lesions, obviating the need for invasive primary surgery or systemic treatment regimens in 80% of cases, and allowing for limited need of secondary surgical or adjunctive procedures in cases with a moderate result.