The chemical diffusion coefficients and the solubility limits of iron in copper were determined in the temperature range 650–1050 °C by electron probe microanalysis. Specimens were 99.999&percent; copper single crystals. The diffusion is best described by two regression lines:DFe‐Cu=0.504 exp(−49740/RT) cm2/s for the temperature interval 1050–800 °C andDFe‐Cu=0.091 exp(−46140/RT) cm2/s for the temperature interval 800–650 °C. The solubility of iron in copper is given to logC=2.951−3357(1/T °K) wt&percent; in the temperature range 1050–650 °C.