  We determine the constraints on the isospin and hypercharge of a scalar
electroweak multiplet from partial-wave unitarity of tree-level scattering
diagrams. The constraint from SU(2)_L interactions yields T <= 7/2 (i.e., n <=
8) for a complex scalar multiplet and T <= 4 (i.e., n <= 9) for a real scalar
multiplet, where n = 2T+1 is the number of isospin states in the multiplet.
