Although optic disc drusen have been of interest to ophthalmologists for more than 100 years, their etiology and many aspects of their relationship to other clinical conditions remain obscure. They have been clinically observed in 0.3% of the population, although autopsy studies suggest an incidence of 2%. Drusen are seldom accompanied by visual symptoms; however, decreased vision and visual field changes may occur. The historical and epidemiological aspects of drusen are reviewed; clinical and histological features, as well as special diagnostic techniques (ultrasonography and fluorescein angiography) are discussed in detail.