Computations have been made of the total beta activity of the fission products arising from the slow neutron fission of U235. A curve is given exhibiting the activity per unit fission, for time intervals after fission ranging from 0.01 second to 10 years. This influence function is compared with some published experimental data and with the statistical curve of Way and Wigner. A curve of its integral as a function of the upper limit is also given. This latter curve facilitates estimation of the activity in the particular case where the fission rate has been constant throughout a known time interval. Finally, an influence function for the particular group of fission products consisting of complete and partial chains having volatile first members is given.