The variation over time of the volume of Corynebacterium glutamicum following osmotic upshocks produced by the addition of increasing NaCl quantities was measured by a lightscattering method. During the first seconds the cell volume rapidly decreased. The extent of volume reduction varied between 30% at 1.5 osmol/kg and 65% at 3.3 osmo/kg. In a second phase the cell volume increased again over a time period lasting 10 minutes or more depending on the magnitude of the saline upshock.