A meeting was held at the University of British Columbia on May 28–29, 1990 to honour the many important scientific contributions made by Dr. Hugh McLennan to our understanding of chemical neurotransmission in the brain and spinal cord. The invited speakers were those with whom Dr. McLennan has at one time or another collaborated, and their presentations reflected Hugh's early interest in GÀBA (factor I) as an inhibitory transmitter and his research over the last two decades into the physiology and pharmacology of acidic amino acid receptors.The session on GABA opened with an intriguing discussion by Professor Florey of the history of the isolation and identification of GABA as a neurotransmitter and was followed by papers dealing with the electrophysiological actions of GABA. Professor Curtis discussed its pre- and post-synaptic actions in the spinal cord, while Dr. Mathers presented data derived from GABA-gated chloride channels isolated from cultured neurones. Professor Krnjević was unfortunately unable to attend the symposium.Work presented by Professors Watkins and Lodge and Dr. Curry provided an excellent historical perspective on the birth and rapid development of excitatory amino acid pharmacology, a field to which Dr. McLennan has contributed enormously.Among the topics pertaining to the electrophysiological actions of acidic amino acids was the role of the NMDA receptor both in long-term potentiation (Dr. Collingridge) and in synaptic transmission in the kainic acid-lesioned hippocampus (Dr. Wheal), the effects of antagonists on synaptic transmission in the thalamus (Dr. Hicks), and the modulation by catecholamines of glutamate-induced neuronal excitations (Dr. Marshall).In his closing address Dr. McLennan, with characteristic grace and style, acknowledged the efforts of his co-workers in his many achievements. Those of us who have had the great pleasure of collaborating with Hugh here at UBC or within the scientific community wish him all the best in his retirement.