We report 14 cases of extranodal sinus histiocytosis with massive lymphadenopathy involving a variety of head and neck sites. The patients ranged in age from 3 to 70 years (median, 43 years). Nine cases occurred in women and five occurred in men. The clinical presentation varied depending on the site of occurrence and included nasal obstruction, stridor, proptosis, ptosis, decreased visual acuity, facial pain or tenderness, cranial nerve deficits, mandibular tenderness, and mass lesions. Head and neck sites involved by disease included the nasal cavity, paranasal sinuses, nasopharynx, parotid gland, submandibular gland, larynx, temporal bone, infratemporal fossa, pterygoid fossa, meninges, and orbital region. The majority of patients presented with involvement of more than one site. Nodal involvement was identified in four patients. Special stains for microorganisms were negative. The sinus histiocytosis with massive lymphadenopathy cells demonstrated an immunophenotypic profile supporting derivation from macrophage/histiocytic lineage. Treatment varied and included surgical excision with or without adjuvant therapy (chemotherapy, radiotherapy) or steroids. Several patients required more extensive surgery as a result of extension of their disease to adjacent structures or due to recurrent disease. Twelve patients are alive and either free of disease or have persistent disease. Two patients died, one as a result of complications of disease.