An intermediate boson scheme of weak interactions is proposed within the framework of the SU (6) symmetry theory. Under the assumptions that: (1) the intermediate bosons belong to the IR (irreducible representation) 21; (2) the weak currents belong to the adjoint representation I R 35; and (3) the s- and p-wave semiweak interactions are assigned to the (3*, 1) part of the IR 21 and the (3*, 3) part of the IR 15 respectively, we obtain an effective nonleptonic interaction which gives three sum rules for the s-wave (parity-violating) and one for the p-wave (parity-conserving) decay amplitudes of the hyperons. These relations seem to be well-satisfied by the experimental data.