[en] Results from recent integral decay-power experiments are presented and compared with summation calculations. The experiments include the decay power following thermal fission of ²³³U, ²³⁵U, and ²³⁹Pu. The summation calculations use ENDF/B-IV decay data and yields from Versions IV and V. Limited comparisons of experimental β and γ spectra with summation calculations using ENDF/B-IV are included. Generalized least-squares methods are applied to the recent ²³⁵U and ²³⁹Pu decay-power experiments and summation calculations to arrive at evaluated values and uncertainties. Results for ²³⁵U imply uncertainties less than 2% (1 sigma) for the ''infinite'' exposure case for all cooling times greater than 10 seconds. The uncertainties for ²³⁹Pu are larger. Accurate analytical representations of the decay power are presented for ²³⁵,²³⁸U, and ²³⁹Pu for use in light-water reactors and as the nominal values in the new ANS 5.1 Draft Standard (1978). Comparisons of the nominal values with ENDF/B-IV and the 1973 ANS Draft Standard in current use are included. Gas content, important to decay-heat experiments, and absorption effects on decay power are reviewed. 37 figures, 8 tables