Lessons from the light-cone box

Working in the noncovariant light-cone gauge, we discuss the explicit compu tation of the 1PI four-point function ("box diagram") in Yang-Mills theory. The complete box diagram which consists of 16 box subdiagrams, 8 lynx subd iagrams and 4 fish subdiagrams, yields both local and nonlocal UV divergent terms. The nonlocal terms are consistent with gauge symmetry and correspon d to a nonlocal renormalization of the wave function.