The separation ability and zone broadening effect in mobile phase have been studied by using GPC columns packed with nonporous glass beads．Polymer samples of different molecular weight could be separated to some extent on these colunlns．Kelley and Billmeyer indicated that the theoretical plate height describing zone broadening effect in mobile phase depends on the’molecular weight of solute only．However．the width of peak was found to be different in samples of the same molecular weight but of different molecular weight distribution in the present inves-tigation．The reverse flow zone broadening factor，h，of benzene is somewhat larger than the straight through flow zone broadening factor，h’．This may bd explaned by the fact that the velocity profile of flow was disturbed during reverse flowing．In GPC columns packed with porous silica beads the dependence of reverse flow zone broadening factor，h，on elution volume，Ve，has been examined for a series of samples of different chemical structure，different molecular weight and different mole-eular weight distribution． Experimental results showed that the relation between h and Ve is universal，independent of chemic al structure of polymer samples in agreement with Tung’s．h>h’was also found for benzene in columns with porous packing．This indicates that the use of h value obtained from the reverse flow method mny lead to slight underestimation of the zone broadening effect in GPC．The shape of reverse flow elution curve was found to be very close to Ganssian only for polymer samples with narrow molecular weight distrihIution within the pre-meation limit of the column used．