[en] The new isotope 178Tl was produced in a bombardment of 102Pd by 78Kr ions at 340 MeV. Reaction products were separated from the beam by the Berkeley Gas-Filled Separator and implanted into a silicon strip detector where the subsequent alpha decays were measured. Four distinct alpha transitions from 178Tl were observed correlated to 6.54 MeV alpha decays from the previously known 174Au daughter. In some cases, the 174Au decay was followed by a 5.815 MeV alpha decay. This new transition is tentatively assigned to the decay of the 170Ir ground state. The half-life of 178Tl was measured to be 254 ms. The alpha decay branch of 174Au was determined to be 90(6) percent