Precipitation in Cu-0.43 at.%, 0.56 at.% and 2.6 at.% Fe alloys was studied by electron microscopy. Coherent γ-Fe, partially coherent γ-Fe, non-coherent γFe and non-coherent α-Fe precipitates were observed. The size distributions of coherent γ-Fe precipitates were found to be in good agreement with theoretical distributions of the bulk diffusion case in Ostwald ripening. The interfacial energy of γ-Fe precipitates was evaluated as 0.3±0.1 J/m2. Average sizes of γ-Fe precipitates in thin foils which were thinner than about 20μm, were much larger than average sizes in thick foils. This thickness effect appears because the precipitation is enhanced by dislocations introduced by quenching.