The generation of tritium was quantitatively measured in an electrolytic cell with a nickel cathode and a platinum anode in potassium carbonate-light and heavy water solutions. Simultaneously, the evolution of a large amount of excess heat (70 to 170% for the input power) was observed during electrolysis of these solutions. The tritium generation by electrolysis provides some of the most conclusive evidence for so-called cold fusion, along with the calcium generation described in a previous paper. On the basis of the current experiments and the knowledge of the kinetics of a hydrogen evolution reaction in an alkaline solution, the nuclear reactions taking place are worth mentioning.