  We discuss the three-body decays stop_1 -> W^+ b neutralino_1, stop_1 -> H^+
b neutralino_1, stop_1 -> b slepton_i neutrino_l, and stop_1 -> b sneutrino_l
l^+$ ($l =e,\mu,\tau$) of the lighter top squark within the minimal
supersymmetric standard model. We give the complete analytical formulas for the
decay widths and present a numerical study in view of an upgraded Tevatron, the
CERN LHC, and a future lepton collider demonstrating the importance of these
decay modes.
