Equations were developed and calculations were made to determine the effective contributions of delayed neutrons in the MSRE during steady power operation. Nonleakage probabilities were used as the measure of relative importance of prompt and delayed neutrons, and the spatial and energy distributions of the prompt and delayed neutron sources were included in the calculation of these probabilities. Data which indicate a total yield of 0.0064 delayed neutron per neutron were used to compute total effective yields of 0.0067 and 0.0036 for the MSRE under static and circulating conditions respectively. (auth)