Specimens of human cerebral cortex were obtained during neurosurgical operations and studied by immunocytochemistry and electron microscopy, using antibodies to the GABA transporter GAT-1. Cortical material from macaque monkeys was prepared similarly. Large numbers of GAT-1-positive non-pyramidal neurons were observed in layers I, II, V, and VI of the cortex. Electron microscopy also showed that the GAT-1-positive axon terminals formed symmetrical and not asymmetrical synapses, suggesting that they were the terminals of non-pyramidal neurons. Processes of cells in the walls of blood vessels were also labelled. We conclude that GAT-1 is present in cell bodies and axon terminals of non-pyramidal neurons, and a population of mural cells in blood vessels, in the primate cerebral cortex.