A Fleischmann & Pons‐type experiment was performed making use of ten electrolytic cells electrically connected in series with constant current crossing them. The experiment lasted about three months during which the maximum current value reached was 2.5 A corresponding on the avearage to 500 mA/cm2. Neutrons, tritium in the solution and in the recombined gases, &ggr; ‐ray and temperature of the electrodes were measured. For about ten days, when the current density was set over 320 mA/cm2a remarkable increase of the neutron detector counting‐rate with respect to the background level (2 counts/h) was observed. The pattern of the emission was burst‐type. In the first part of that period, we found in three cells out of nine (one of the ten cells was in light water) a significant excess of tritium with respect to the expected value calculated for the electrolytic enrichment. The other cells, included that in light water, did not show any excess of tritium the value of which was in very good agreement with the calculated value.