Discovered in 1981, bilirubin oxidase (BOD) became an important cathode enzyme in design of biofuel cells (BFCs). Substantial catalytic activity at neutral pH, minor inhibition by chloride ions and high-redox potential of the T1 copper site, being close to the redox potential of oxygen reduction to water, are the advantageous characteristics that distinguish this enzyme from other multicopper oxidases, for example, laccases, used in design of BFC cathodes. This article discusses the basic concept of BFCs and summarizes the achievements and limits which are reached by BFCs with focus on cathodes modified by BOD. Enzymatic cycle in homogeneous media and direct and mediated heterogeneous electron transfer of BOD are briefly summarized.