Hemangiopericytoma (HPCT) rarely originates in the lacrimal sac; 7 cases have been reported previously and only 1 contained an ultrastructural study. In this article we report an additional case and review the previous reports. While the initial biopsy specimen showed nonspecific cytologic abnormalities, light and electron microscopic studies on the subsequently excised tumor demonstrated that it had a structure characteristic of HPCT. The onset of lacrimal sac HPCT occurs in a younger age group than that of HPCT of other orbital locations. The tumor may recur locally but, to our knowledge, never has been reported to metastasize from a sac location. The treatment goal is complete surgical excision.