Viscosities and number average molecular weights of various carrageenin preparations, including thermally and photochemically degraded samples, have been measured. Aqueous solutions of carrageenin of low molecular weight are shown to exhibit viscosity characteristics which are entirely similar to those of other natural and synthetic polyelectrolytes. Solutions of carrageenin of high molecular weight exhibit plastic flow. The relationship between viscosity and molecular weight for the degraded polymer indicates that the molecular configuration in solution is that of a fairly stiff rod, even in the presence of salts.