The need for surgical repair of monocanalicular lacerations is controversial. The authors used temporary punctal plugs of hydroxypropyl cellulose to assess the symptoms associated with upper and lower monocanalicular obstruction in 18 normal eyes. Fifty percent of those experimental obstructions resulted in mild intermittent symptoms of epiphora, increased tear film, discomfort, or blurred vision. Constant epiphora was not reported. The results suggest that a single upper or lower canaliculus is sufficient for drainage of minimally stimulated tear secretion but may not completely drain reflex tear secretion. This information may help patients and ophthalmologists reach an informed decision as to the need for surgical repair of a severed canaliculus.