We show that proper Dupin
hypersurfaces Mn for n ≥ 4 in ℝn+1 with n distinct principal curvatures and
constant Möbius curvature cannot be parametrized by lines of curvature. For n = 3,
up to Möbius transformations, there is a unique proper Dupin hypersurface,
parametrized by lines of curvature, with three distinct principal curvatures and
constant Möbius curvature. Moreover, these hypersurfaces are the only conformally
flat proper Dupin hypersurfaces M3⊂ ℝ4 with three distinct principal curvatures
and constant Möbius curvature.