The potential energy surfaces of H2NBH2 and PF3 in the regions of the hindered internal rotation in aminoborane and the inversion in trifluorophosphine have been studied in terms of the gradient line (steepest-descent) reaction pathways. We find that the gradient line reaction path for the aminoborane internal rotation consists of two equivalent paths separated in configuration space; the gradient line reaction path for the PF3 inversion consists of three equivalent reaction paths. Hence, the aminoborane internal rotation and the AF(3) (A = P, Sf, Sb, As, Bi) inversion are fundamentally multidimensional processes.