The effects of matrix/precipitate interface states on coarsening of Co and gamma-Fe precipitates in a Cu-4 wt.%Co and a Cu-2 wt.%Fe alloy aged at 500 and 700C have been examined by transmission electron microscopy (TEM) observations, electrical resistivity measurements, and length-change measurements. Analyses of TEM images show that the average radius for coherent/semi-coherent transition is 6-12 nm for the Co precipitates and 10-20 nm for the gamma-Fe precipitates. The coarsening rates of the Co and gamma-Fe precipitates are unchanged by the transitions in coherency of the precipitates. The interface energies gamma of coherent Co and gamma-Fe precipitates are estimated from data on coarsening alone as 0.15 and 0.27 J m(-2). From length-change measurements of the Cu-Co and Cu-Fe alloys during aging, the estimates of the isotropic misfit strains of Co and gamma-Fe precipitates are -0.018 and -0.016 for the coherent interfaces and -0.013 and -0.012 for the semi-coherent interfaces. Free energy analyses for the coarsening of Co and gamma-Fe precipitates reveal that the values of gamma of semi-coherent Cu/Co and Cu/gamma-Fe interfaces are 0.24 and 0.34 J m(-2).