Sucrose-grown (unadapted) and succinate-grown (adapted) cells were mixed with various concentrations of succinate at 3 °C. under air and at 30 °C. under helium. The amount of succinate removed from the external solution by the cells was proportional to the concentration of succinate and did not differ significantly with the two types of cells. Although the data did not differentiate between equilibration with intracellular water and mere adsorption, they indicate that no change has occurred in the surface of the adapted cells to allow a more rapid diffusion of succinate across the osmotic barrier under nonmetabolic conditions. So far as can be determined by using masses of cells, any "permeability" changes during adaptation of the azotobacter cells to succinate must be connected with an active transport process associated with metabolism.