  We discuss doping dependencies of the electronic structure and Fermi surface
of the monolayer Tl$_{2-x}$Cu$_x$Ba$_2$CuO$_{6+\delta}$ (Tl2201). The TlO bands
are found to be particularly sensitive to doping in that these bands rapidly
move to higher energies as holes are added into the system. Such doping effects
beyond the rigid band picture should be taken into account in analyzing and
modeling the electronic spectra of the cuprates.
