Description: This paper deals with the selection of appropriate interest and inflation assumptions, which is one of the most important considerations in the valuation of a defined benefit pension plan. The paper begins by describing a simplified model in which the only important consideration is the selection of an appropriate differential between interest and inflation assumptions. The discussion then considers some situations that might lead the actuary to attempt to select a realistic level of interest and inflation assumptions, in addition to an appropriate differential. The author's conclusion is that in some situations the absolute level of the interest and inflation assumptions can be all but meaningless, and the differential between the two assumptions is the important factor. In other situations the use of this technique will produce serious inaccuracies in the valuation results. As always, the actuary must analyze each situation in order to determine which of the available techniques will produce the best results with the least effort, given the degree of accuracy required. From Transactions of Society of Actuaries 1976, Vol. 28.