A macroscopic model for calculating fission barriers (saddle-point energies) in two versions: with and without accounting for shell effects, is presented. Results of calculations with shell effects switched off agree very well with previous purely macroscopic calculations done by A.J. Sierk. Complete calculations of fission barriers (including shell effects) are done for nuclei in the range 66 \leq Z \leq 100, for all isotopes with experimentally determined barrier heights. With a value of the shell-energy-damping parameter that fits the ground-state masses of deformed nuclei, shell effects almost completely disappear at the saddle configuration, thus leading to a strong manifestation of the ground-state shell effects, in agreement with experimental data.

PACS numbers: 25.85.--w