The edible clams from Lake Timsah are exposed to different industrial wastes which may reflect the reason for the high concentration of heavy metals in studied species. The current study aims to evaluate the effect of size classes on the elimination of heavy metals (Cu, Fe, Pb, Co, Ni, and Zn) in some commercial bivalves Ruditapes decussatus, Venerupis pullastra and Paphia undulata. Negative correlations were found between the sizes of studied species for all heavy metals (except Cu which showed a positive correlation with size in V. pullastra). The concentrations of all heavy metals (Cu, Fe, Pb, Co, and Zn) in the studied species were higher than those in water and sediment. The highest depuration rate for all studied species was recorded in small clam classes.