  We consider the quantum ferromagnetic transition at zero temperature in clean
itinerant electron systems. We find that the Landau-Ginzburg-Wilson order
parameter field theory breaks down since the electron-electron interaction
leads to singular coupling constants in the Landau-Ginzburg-Wilson functional.
These couplings generate an effective long-range interaction between the spin
or order parameter fluctuations of the form 1/r^{2d-1}, with d the spatial
dimension. This leads to unusual scaling behavior at the quantum critical point
in 1 < d\leq 3, which we determine exactly. We also discuss the
quantum-to-classical crossover at small but finite temperatures, which is
characterized by the appearance of multiple temperature scales. A comparison
with recent results on disordered itinerant ferromagnets is given.
