A 49-y-old male, who had travelled in Central Africa, was admitted to hospital with oedema of the right forearm. He was diagnosed as having thrombosis of the ulnar veins. Subsequently eosinophilia and positive serology for filariae established the aetiologic agent as Loa loa. The patient received antithrombotic and antiparasitic therapy. This is, to our knowledge, the first reported case of thrombosis of the ulnar veins associated with Loa loa.