Structural and x-ray photoelectron spectroscopy (XPS) studies of the Tl1-xPbxSr1+xLa1-xCuO5-y (0.0≤x≤0.5) system have been carried out. The unit cell parameters increase with x. Irrespective of x the Tc is retained in this series and the optimum hole concentration (nh) is maintained for x≤ 0.5. An increase in Tl 4f and O ls binding energy with x suggests a reduction in their oxidation state. Origin of holes is discussed in terms of charge transfer between Tl, Pb and CuO2 layers. © 1998 Plenum Publishing Corporation.