The fourth branchial pouch sinus is a congenital anomaly which most frequently manifests itself by recurrent episodes of neck abscess or acute suppurative thyroiditis. This lesion usually becomes symptomatic before the age of 10 years and is more common than has previously been suspected. It has been found on the left side in 93% of the 28 cases reported in the English literature. Barium swallow during periods of quiescence and nasopharyngoscopy have frequently been successful in identifying the presence of these embryological remnants. Definitive therapy consists of total excision of the sinus tract, which can be facilitated by direct endoscopic placement of a Fogarty catheter into the sinus lumen before surgical exploration. The embryological basis for the occurrence of these sinuses is discussed.