The melanin pigmentation of 18 subjects was investigated in vivo by measuring light (λ = 675 nm) reflected from an area of 7° × 7° of the fundus incorporating the macula. The mean value for 16 Caucasian fundi was 0.79 ( ± 0.17) extinction units (E). The value for an albino (E = 0.06) and a Negro fundus (E = 1.36) lay well outside the range of Caucasian values. The in vivo results are in good agreement with measurements made on enucleated eyes