Serum albumins are chief carrier of ligands in blood, hence important in clinical biotechnology. The effects of methyl cyanide (MeCN), a chief solvent of reverse phase chromatography, on four mammalian serum albumins (human, bovine, porcine and rabbit sources) were studied at neutral pH with the help of scattering, circular dichroism, IR and fluorescence spectroscopy. We have detected an intermediate state in the presence of 20% (v/v) MeCN, having 8-9% higher alpha-helical structure than that of their native states. In the presence of 60% (v/v) MeCN another intermediate was observed with non-native beta-sheet structure and high tendency to form aggregates.