Beam-beam effects in the Tevatron

The Tevatron in Collider Run II (2001--present) is operating with 6 times more bunches, many times higher beam intensities and luminosities than in Run I (1992--1995). Electromagnetic long-range and head-on interactions of high intensity proton and antiproton beams have been significant sources of beam loss and lifetime limitations. We present observations of the beam-beam phenomena in the Tevatron and results of relevant beam studies. We analyze the data and various methods employed in operations, predict the performance for planned luminosity upgrades, and discuss ways to improve it.