• A 17-year-old girl with right-sided epiphora and a lacrimal sac mass was found radiologically to have marked enlargement of her lacrimal sac and nasolacrimal duct and mucosal thickening of her right nasal turbinates and maxillary, ethmoid, and sphenoid sinuses. Biopsy specimens from all these sites showed chronic inflammatory infiltrates with a predominant population of large phagocytic histiocytes, some of which had engulfed lymphocytes and plasmacytes. The results of a systemic workup were normal. This is the first reported case, to our knowledge, of sinus histiocytosis involving the lacrimal sac and nasolacrimal duct as an extranodal focus.