The loss from polypropylene (PP) of sterically hindered amines with molecular weight ranging from 1364 to 2758 in heptane, chloroform, and methanol at room temperature was studied. The additives leak from polymer in heptane and in chloroform and some residual concentration remains in the polymer; the stabilizers show slight migration in methanol. The rate of loss increases with additive concentration in the polymer. The effect of solvent during washing out could be explained by its different solubility in PP resulting in changes in polymer chain mobility and additive migration from the polymer.