Two cases presented with solitary cystic mass in the usual position of a branchial cyst in the neck are reported. Histology on both cysts reported as carcinoma of a branchial cyst (malignant branchioma). In addition to pre-operative radiotherapy to the neck, and ipsi-lateral radical neck dissection, the oropharynx is irradiated in prophylactic manner only in the second case. The first patient died of tonsillar carcinoma 3.5 years after diagnosis and the second case is well with no sign of recurrence 4 years after the initial diagnosis. The authors discuss the nature and management of the so called malignant branchioma.