Exchange bias is a phenomena associated with magnetization and hysteresis in ferromagnet/antiferromagnet bilayers. Prospects for control and enhancement of exchange bias effects make it important for applications to several spin electronic devices, and requires a clear understanding of underlying mechanisms. A general theoretical formulation of the bias problem in terms of partial magnetic domain wall formation and pinning is outlined. A key result is the existence of higher order coupling terms when more than one sublattice of the antiferromagnet is present at the interface. Results from calculations of finite temperature effects on bias and coercivity are described, and the concept of viscosity in the antiferromagnet is discussed. (C) 2002 Elsevier Science B.V. All rights reserved.