A young girl with an arteriovenous malformation involving the right upper extremity developed rapidly progressive bony destruction that did not respond to embolization. Treatment with marimastat, starting at 3 years of age, resulted in rapid resolution of pain and gradual healing of bony destruction, associated with regression of the intraosseous arteriovenous shunts. New arteriovenous shunts with bony destruction developed over the years and responded to an increase in the dose of marimastat. Interruption of therapy resulted in recurrence of pain and formation of new lesions. The patient has been treated in this way for 12 years with no adverse effects from the drug.