This paper investigates the possibility of CO2 laser welding austenitic stainless steel to copper. The experimental results show that solidification cracking may be the greatest problem in this application. It is suggested that the cracks are generated in three ways: Liquid metal embrittlement, due to the presence of copper in the solidifying steel grain boundaries. Stresses generated during solidification due to fixturing and differences in the thermal properties of the materials involved. A solidification mode change due to the rapid weld solidification involved in laser welding of austenitic stainless steel. To overcome these problems the fixturing and specimen edge preparation have to be optimized to minimize the amount of copper in the fusion zone, to reduce the stresses, and to minimize the cooling rate during solidification. These factors were taken into account and the resulting welds were of high integrity with the same strength as the original copper being welded. The role of thermocapillary or Marangoni flow in transferring heat to the copper side of the weld is also discussed