The low-deformation extension modulus was measured for Ca-alginate gel fibers prepared from alginates of different compositions and molecular weights. The modulus showed an increase with increasing molecular weight for alginates of the same composition and sequence parameters. Fibers prepared with an inhomogeneous polymer concentration profile showed higher moduli than did fibers with a homogeneous polymer concentration profile. The higher modulus observed for fibers prepared from an alginate with low Ca2+ affinity is tentatively explained as resulting from a higher degree of polymer chain alignment.