Every three years early Spring witnesses the convening of a small group of neuroscientists from many parts of the world. They are devoted to the study of acetylcholine, the oldest of the known neurotransmitters. To assess the level of knowledge, to take stock of the still unsolved problems, to evaluate the practical meaning of their findings, the cholinologists first met in 1969 in the eerie atmosphere of a snow-covered Swedish forest, the second in the Swiss Alps, the third facing the surf and foam of the Paci- fic waves. Finally in March 1980 Florence, her trees burgeoning in the mild rain of March, confronted them with the temptation of her monuments and museums. But the cholinologists bravely dismis- sed the temptations and went on with the presentations and discus- sions of the many papers which form the present book. The papers describe the most recent development of investiga- tions on acetylcholine. They open with an extensive coverage of the developmental and phylogenetic aspects of the cholinergic neurons. The regulation of acetylcholine synthesis, release, post- synaptic, electrical and trophic effects in the peripheral chol- inergic synapses including ganglia, neuromuscular junction, myen- theric plexus and heart is then covered. Special emphasis is given to the cholinergic mechanisms in the eye.