Abstract— δ‐Aminolevulinic acid (δ‐ALA) was taken up by rabbit brain cortical slices to a concentration greater than that in the surrounding medium. The process responsible for this accumulation of δ‐ALA shows many of the properties characteristic of an active transport system. δ‐ALA is taken up by a system which exhibits some allosteric kinetic properties, and is specific to a relatively high degree.