Protein-adsorbed dialysis membranes are evaluated with time-of-flight secondary ion mass spectrometry (TOF-SIMS) chemical imaging technique. Protein adsorption causing permeability change is one of big issues in the development of dialysis membranes. Bovine serum albumin adsorption onto three kinds of dialysis membranes has been evaluated with TOF-SIMS. In the present study three kinds of proteins, bovine serum albumin, alpha-chymotripsinogen A, and cytochrome C adsorbed onto hollow-fiber dialysis membranes, were measured by means of TOF-SIMS and then TOF-SIMS spectra were analyzed using mutual information. Then specific peaks of fragment ions related to alpha-chymotripsinogen A and bovine serum albumin were found, respectively. In this condition, however, specific peaks to cytochrome C were not able to find compared with other samples. Finally, chemical images of alpha-chymotripsinogen A and bovine serum albumin, respectively, adsorbed onto the membranes with coexisting proteins were obtained. The results of TOF-SIMS images of the proteins on the membranes show different tendency of adsorption depending on co-existing proteins. Further study is needed to study more detailed protein adsorption onto the membranes with co-existing proteins. (c) 2006 Elsevier B.V. All rights reserved.