TH E wing of minimum induced resistance for a given span and lift was first determined b y M . Munk. 1 I t is characterized by the property t ha t the induced velocity w perpendicular to the direction of flight velocity V is constant over the span b and, as a consequence, the circulation function V is given by an ellipse if the span b, the total lift L, the velocity of flight V, and the distribution of drag angle 8 is prescribed. As the parasite drag angle 8 increases with the thickness ratio of the airfoil and therefore increases toward the middle of the span it will in general not be constant and will have to be deduced from experiments, taking account of the scale of the dimensions and the s ta te of the surface of the wing. Besides i t may be mentioned tha t 8 in the range of small angles of incidence a is nearly independent of a and increases outside of it. The theory given here t reats the wing as a fixed vortex line with circulation varying along the span, this variation being produced by a free vortex sheet left behind the trailing edge of the wing. v. Karman 2 and R. Fuchs 3 have shown tha t the theory can be extended to fixed vortex sheets corresponding to the profile of the wing. These papers like t ha t of Munk, are concerned only with the pure induced resistance. The question whether the theorems found by v. Ka rman and by Fuchs can also be generalized for parasite drag, is not t reated here.