During protein separation using the toroidal coil centrifuge, the partition efficiency was found to vary according to the direction of the elution through the coil. In most cases, eluting either the lighter phase toward the direction of rotation or the heavier phase in the opposite direction produced higher efficiencies. The cause of this unusual phenomenon may be attributed to the Coriolis force acting on the mobile phase in the rotating coil. Using a flow-through glass vial and colored mobile phases, the effects of the Coriolis force on moving droplets were observed under stroboscopic illumination. As expected, the path of the descending droplets (heavier phase) shifted against the direction of rotation whereas that of the ascending droplets (lighter phase) shifted toward the direction of rotation. The effect of this Coriolis flow on the partition efficiency was studied with a set of toroidal coils with various core diameters.