Sulfobetaines of two types and the corresponding cationic monomers were synthesized; the preparation of their polymers is described. The solubilities and moisture regain properties of the poly(sulfobetaine)s and cationic polymers were investigated in relation to their molecular structures. It was very difficult to distinguish in H-1 nuclear magnetic resonance (n.m.r.) and C-13 n.m.r. spectra the chemical shift of the methylene moiety (-CH2-) in the neighbourhood of the quaternary ammonium group. By comparison of the chemical shifts of the corresponding cationic monomers and sulfobetaines in both H-1 and C-13 n.m.r. spectra, the respective methylene groups were clearly distinguished from their chemical shifts in the H-1 and C-13 n.m.r. spectra; the conformations of sulfobetaines and the form of cationic monomers in aqueous solution were identified.