The effects of DL-alpha-tocopherol and DL-alpha-tocopherol succinate on neuroblastoma N1E 115 cells were studied. Tocopherol had no growth-arresting properties, whereas its succinate ester derivative inhibited growth at concentrations greater than or equal to 20 microM. The succinate derivative was taken up somewhat more readily than free tocopherol; however, for any equal uptake of both forms of vitamin E, only the succinate derivative could affect growth. Tocopherol succinate was taken up without marked conversion to tocopherol. Following uptake, plasma membrane and organelle fractions contained most of the vitamin E derivatives; however, the particulate and membrane fractions were about twice as enriched in the succinate derivative as in free tocopherol. On the other hand, a proportionally higher amount of unconjugated vitamin E was recovered in the cytosol fraction. Fluorescence polarization studies indicated no differences in the overall fluidity of the plasma membranes treated or not treated with either form of vitamin E. The data point to the functionality of the free carboxyl group of the succinate derivative as a basis for the difference in potency of the two forms of vitamin E.