The fusion-fission process for synthesizing superheavy elements is studied on the basis of the dissipative dynamics. We use a multi-dimensional Langevin equation for the first stage where the reaction system evolves from the contact configuration of two incident nuclei to the later time when the complete dissipation of the initial relative kinetic energy is accomplished, and a two-dimensional Smoluchowski equation for the following stage. The evaporation residue cross sections for superheavy elements have been shown to have an optimum value at a certain initial energy, due to the balance between the diffusibility for fusion at high temperature and the restoration of the shell correction energy against fission at low temperature. The isotope dependence is also discussed. ©1998 American Institute of Physics.