The results of a measurement of periods and yields of delayed neutrons from “fast” fission of 237Np, 238Pu, 241Am, 233U, 240Pu, and 241Pu are presented. For the first three nuclides, only a few incomplete experimental data have been published, while for the others, relatively great discrepancies exist among the data. The present results are given in Keepin's six group representation. Since our instrumentation did not allow measurement of the yield in the sixth group, the values were calculated. The total yields obtained as the sum of the group yields are The consistency with known systematics of the total yields of delayed neutrons was checked and found generally to be good. When possible, the results were compared with those recommended by Tuttle in a recent compilation. The total yields of 240Pu and 241Pu were in very good agreement, but not for 233U. The agreement of the group yields was generally poor.