Abstract The impairment by inositol deprivation of the α-aminoisobutyric acid (AIB) transport system of KB cells was studied under various experimental conditions. Kinetic studies under nonsteady state conditions showed that inositol deprivation causes a decrease of the Vmax of AIB influx and efflux without affecting the respective Km values. The Km for AIB influx is 0.4 to 0.5 mm, whereas for AIB efflux it is 6.2 to 6.8 mm, in both normal and inositol-deficient cells. The AIB efflux coefficients are much lower in deficient cells at all levels of intracellular AIB. When AIB exchange fluxes were studied under steady state conditions it was found that inositol deprivation causes a decrease of the influx coefficient and the Vmax. Active AIB transport requires the presence of extracellular Na+. The effect of decreasing the extracellular Na+ concentration is to increase the Km for AIB uptake without affecting the Vmax. This increase is greater in normal (11.0 mm) than in deficient cells (1.5 mm). Active AIB transport and accumulation are inhibited by ouabain. Half-maximal inhibition is obtained at 0.35 µm for AIB uptake and 0.1 µm for AIB accumulation, with both types of cells. The fraction of AIB transport sensitive to ouabain is 62% in normal and 38% in deficient cells. However, ouabain abolishes active transport in both types of cells. It is suggested that inositol deprivation impairs AIB transport because of structural alterations at the carrier sites of the plasma membrane.