A short, monodisperse additive (octa(ethylene glycol) monophenyl ether) functions to suppress aggregation of thermally and chemically denatured lysozyme. Control studies with shorter and non-amphiphilic derivatives revealed that the amphiphilic structure is essential, and octa(ethylene glycol) is nearly the minimum chain length for amphiphilic poly(ethylene glycol)s to stabilize proteins.