UNLABELLED: PURPOSE; To investigate the underlying causes of acquired external punctal stenosis (AEPS) and assess the associated tear drainage problems. DESIGN: Prospective, noncomparative observational case series. METHODS: Seventy-eight eyes of 52 patients with symptomatic AEPS were prospectively assessed by or under supervision of a consultant oculoplastic surgeon from June 1999 to October 2002. The severity of the stenosis was graded on clinical examination. Associated findings from ophthalmic examination, diagnostic probing, and irrigation were recorded. The chi(2) test with 95% confidence interval (CI) and the Fisher exact test were used for statistical analysis. RESULTS: The age range was 39 to 90 years (mean, 69.4 years). Acquired external punctal stenosis was due to chronic blepharitis in 35 eyes (45%), unknown etiology in 21 eyes (27%), ectropion in 18 eyes (23%), and related to drugs in 4 eyes (5%). Associated canalicular stenosis and common canalicular stenosis with obstruction (at the level of the internal punctum) was found in 36 eyes (46%) with AEPS. Nasolacrimal duct stenosis (5 eyes) or obstruction (2 eyes) was found in 8.5%. The number of patients with associated canalicular and common canalicular stenosis increased with increasing age (95% Confidence Interval [CI] = 0.03-0.04, P =.03) and duration of symptoms (95% CI = 0.02-0.03, P =.02). The number of patients with associated nasolacrimal duct stenosis and obstruction increased with increasing age (95% CI = 0.000- 0.001, P =.001) and in AEPS with unknown etiology (95% CI = 0.004-0.006, P =.003). CONCLUSIONS: Chronic blepharitis is a common cause of AEPS even after treating the blepharitis, but in a significant number of patients there is no apparent etiology. Associated upper and lower tear drainage stenosis should be considered in the preoperative evaluation and surgical plan for AEPS.