Relations were studied between baker's yeast (Saccharomyces cerevisiae) cell disruption run in a bead mill and the release of intracellular proteins. The cont. phase of the suspension was 0.15 M NaCl and 4 mild K2HPO4 or aq. 0.1% beta-mercaptoethanol contg. 0.01 M EDTA. Various cell sizes made disruption a nonlinear process, which slowed down the solubilization of proteins. Disintegration reduced and release of proteins increased the apparent viscosity. The release of proteins can be described by a nonlinear model based on mass transfer.