Macular degeneration is a common cause of blindness in the elderly. To identify rare coding variants associated with a large increase in risk of age-related macular degeneration (AMD), we sequenced 2,335 cases and 789 controls in 10 candidate loci (57 genes). To increase power, we augmented our control set with ancestry-matched exome-sequenced controls. An analysis of coding variation in 2,268 AMD cases and 2,268 ancestry-matched controls identified 2 large-effect rare variants: previously described p. Arg1210Cys encoded in the CFH gene (case frequency (f(case)) = 0.51%; control frequency (f(control)) = 0.02%; odds ratio (OR) = 23.11) and newly identified p. Lys155Gln encoded in the C3 gene (f(case) = 1.06%; f(control) = 0.39%; OR = 2.68). The variants suggest decreased inhibition of C3 by complement factor H, resulting in increased activation of the alternative complement pathway, as a key component of disease biology.