Description: Private defined benefit pension plans must, by law, pre-fund the retirement benefits. This requires the periodic valuation of liabilities and calculation of contributions. Because valuation assumptions are seldom borne out by reality, a surplus [or deficit] ensues and varies over time. When the surplus becomes sizable, there often arises a desire to distribute part of it so as to bring it down to a more reasonable level. This paper provides a brief overview of cooperative game theory and, in particular, sharing rules. Then, using certain sharing rules, it determines how to split the surplus or deficit among the plan participants and sponsor. In general, the participant's share in the surplus depends on the total of his contributions. Other considerations, such as the actual investment income received on his contributions or the years of service, may influence the distribution of the surplus. It may even appear desirable to take account of the accrued liability. From Actuarial Research Clearing House 1998, Vol. 1.