While mechanical obstruction of the nasolacrimal duct is the most common cause of acquired unilateral epiphora, it is not the only one. Of the 94 patients evaluated with this symptom, 22 cases (23%) were caused by primary nasal changes in the form of nasal allergy. Many of the characteristic findings of mechanical obstruction were present. Several patients had previous nasolacrimal duct surgery, which failed to eliminate the epiphora. Nasal allergy was not initially considered either by previous examiners or the patients themselves, because of the absence of typical allergic symptoms. All of these patients, however, obtained relief from their unilateral tearing with treatment directed toward the nasal pathology only. Oral sympathomimetics and antihistamines were the most effective. Two patients improved with primary nasal surgery.