The total delayed neutron yield for sup 238 U and sup 241 Pu were observed as a function of the incident neutron energy. The measurements extend from 2.5 to 5 MeV for sup 238 U and from 0.15 to 5 MeV for sup 241 Pu. The average ratio of the sup 241 Pu delayed neutron yield to that of sup 238 U is 0.292 +- 0.022.