A detailed study of the interdiffusion and resistivity of Cu/Au, Cu/Co/ Co/Au and Cu/Co/Au thin film structures was carried out at temperatures ranging from 25 to 550°C1. Both Cu and Au, in the Cu/Au structure, intermix readily even at temperatures as low as 150°C and the interdiffusion is accompanied by rapid increase in resistivity. Very little interdiffusion occurs in the Cu/Co, Co/Au or Cu/Co/Au thin film structures up to about 400°C, after which the resistivity increases. The very rapid increase in resistivity observed at 250°C for the Cu/Au system and at 450°C for Cu/Co/Au, is associated with recrystallization of the films into large grains and the formation of AuCu, Cu3Au and Cu3Au2 compounds. The Cu/Co/Au structure recrystallizes at a higher temperature because of the time needed for Cu and Au to diffuse through the Co layer, which did not react significantly with either Au or Cu.