We study the structure of weakly compact homomorphisms between Banach algebras. In particular, it is shown that between many pairs of algebras, the only weakly compact homomorphisms are those of finite rank. Problem 1.1. Let A and B be Banach algebras. If 6 : A-> B is a weakly compact homomorphism, then do there exist a reflexive Banach algebra C and continuous homomorphisms cp : A-> C and i// : C-> B such that 9 = y/ o cp ? The corresponding statement for linear maps between Banach spaces is known to be true (see e.g. [5; 15, Theorem 2.g.l 1]), but its proof fails to adapt to our situation because the interpolation method used does not respect Banach algebras.