Evidence for tritium production in the Pd/D system under cathodic polarization is presented. A comparison of the observed distribution and that calculated, based on the conservation of mass, leads to the conclusion that tritium is produced sporadically at an estimated rate of ~103 to 104 atom/s. The results of several runs are interpreted by employing the concept of an electrode/electrolyte interphase and the accepted kinetics of hydrogen evolution. Burstlike events followed by longer periods of inactivity yield poor reproducibility when distributions are averaged over the total time of electrolysis.