Thermomigration ͑TM͒ in Sn58Bi solder was detected in Cu/Sn58Bi/Ni solder joints supplied with direct current. Thermal electric finite-element simulation showed that a thermal gradient of 527°C / cm existed in a solder joint when a current density of 5 ϫ 10 3 A / cm 2 was applied to the structure at 50°C. Depending on the direction of the current, TM was found to assist or counteract electromigration ͑EM͒ on the diffusion of Bi atoms. The atomic fluxes of Bi induced by EM and TM were estimated separately. EM-enhanced cross interaction between Cu and Ni across the solder joint was also detected, which led to the intermetallic compound ͑IMC͒ at Ni side or the Cu side of the joint that electron flow was from the Cu side to the Ni side is thinner than that of corresponding IMC in the joint stressed with current in opposite direction. For the joint as reflowed, the IMC at the Ni side was ͑Cu, Ni͒ 6 Sn 5 instead of Ni 3 Sn 4 and the IMC at the Cu side was Cu 6 Sn 5 without Ni atoms contained. When Ni wire set as anode, the IMC at the Ni side was still ͑Cu, Ni͒ 6 Sn 5 even after the joint was stressed for 384 h. However, it turned into ͑Ni, Cu͒ 3 Sn 4 if Ni wire set as cathode. Regardless of the directions of the electric current, the IMC at the Cu side was Cu 6 Sn 5 at all time. For the joint that Cu wire set as anode, the growth of Ni 3 Sn 4 at the cathode side was enhanced by EM and TM, while the growth of Cu 6 Sn 5 at the anode side was retarded.