SUMMARY A single permease is responsible for the active transport of L-glutamate, L-aspartate and L-cysteate in Aspergillus nidulans. Apparent K, values are I 80 p~, IOO ,UM and 190 ,UM respectively. The transport of glutamate occurs against a con- centration gradient of at least I : 200, is inhibited by azide and cyanide, and shows a pH optimum of 5.0 and a temperature optimum of 45 "C.