Background To determine the prevalence of crowded optic discs and their associations with ocular and general parameters. Methods The Beijing Eye Study included 4,439 subjects out of 5,324 subjects invited to participate (response rate 83.4%) with an age of 40+ years. The present investigation consisted of 8,594 eyes (96.8%) of 4,324 subjects (97.4%) for whom readable fundus photographs of at least one eye were available. The main outcome parameter was the presence of crowded optic discs, defined as small discs with an unsharp and slightly prominent disc border without signs of pathology. Results Crowded optic discs were detected in 265 (3.1 +/- 0.2%) eyes of 168 subjects (84 women). The prevalence rate was 3.8%+/- 0.3% (95% confidence interval: 3.2%, 4.4%) per subject. Crowded optic discs were significantly associated with age (P<0.05%) and disc size (P<0.001). They were statistically not associated with gender (P=0.08), intraocular pressure (P=0.06), refractive error (P=0.17), visual field defects (P=0.53), and best corrected visual acuity (P=0.57). Conclusions Crowded optic discs are present in about 38 out of 1000 adult Chinese in Northern China, with small optic discs as the main associated factor. These data may be helpful for the assessment of a risk for nonarteritic anterior ischemic optic neuropathy.