Luminosity Limitations at Hadron Colliders

I discuss fundamental luminosity limitations at hadron colliders, addressing head-on and long-range beam-beam interaction, empirical scaling, synchrotron radiation, intrabeam scattering, dynamic evolution during the store, flat beams, heat load, power consumption, and electron cloud. Parameters of past or operating colliders - ISR, SPS, Tevatron, RHIC -, are compared with the LHC and further extrapolated to an LHC upgrade and to the VLHC.