The invention provides methods and compositions for determining whether a subject is at risk of developing age-related macular degeneration, for example, the wet or neovascular form of age-related macular degeneration. The method involves determining whether the subject has a protective variant and/or a risk variant at a polymorphic site in the HTRA1 gene. In addition, the invention provides a method of treating or slowing the progression of age-related macular degeneration by reducing the expression of the HTRA1 gene, or reducing the biological activity of the HTRA1 gene product.