During the determination of three unknown structures, the method of optimal selection on the distribution of index among the starting reflections was incorporated with the symbolic addition and the MULTAN procedures respectively. It is proved that the optimal selection method provides a better starting set which in the case of MULTAN leads to increase of the figure of merit corresponding to the correct solution. An example is given that structure which had failed to be solved by MULTAN 78 can be solved successfully by incorporating with the optimal selection method.