The mechanical and swelling properties of alginate gels are studied. Discussion of the results of the dynamic and swelling measurements in terms of the theories of ideal rubberlike elasticity leads to cross-link densities, which are in satisfactory agreement.Stress-strain curves, dynamic measurements on swollen gels and measurements of solution viscosity are used to obtain information about the number of statistical chain elements in a sodium alginate chain. The results show that the number of statistical chain elements in an average strand between cross-links is much smaller than would be required in order to make the theory of ideal rubberlike elasticity applicable. An explanation for the observed “Gaussian” behaviour is suggested, on the basis of a distribution of the “strength” of the cross-links.