  A brief review of lattice calculations of the bag parameter B_K relevant for
understanding indirect CP violation in the neutral kaon sector is given. A
status report on current state-of-the-art calculations is presented as well as
a discussion of the value of B_K exported to phenomenologists. This is a
condensed and updated version of the review presented at the CKM Unitarity
Triangle Workshop held at CERN during Feburary 13-16, 2002
(http://ckm-workshop.web.cern.ch/ckm-workshop/).
