We have determined the scattering length of the a (3)Sigma(+) potential of (RbCs)-Rb-87 based on experimental observations from the literature and the known value for the long-range dispersion coefficient. Our analysis uses quantum defect theory and analytical solutions of the Schrodinger equation for a van der Waals potential. We find that the scattering length is either 700(-300)(+700)a(0) or (176 +/- 2)a(0) with more confidence associated with the first value, where a(0)=0.052 92 nm is the Bohr radius. An independent value of the van der Waals coefficient could not be determined and the best theoretically determined C-6 value was used.