The synaptology of the striato- pallidonigral connection is so peculiar as to be recognized easily. Pallidonigral dendrites are entirely covered with synapses without any apposition of glia. This gives in sections characteristic images of "pallissades" or of "rosettes". More than 90% of these synapses are of striatal origin. The few other synapses such as the dopaminergic or the cholinergic are interspersed among the GABAergic striatonigral synapses. The way striatal axons distribute their synapses is a disputed point. The fact that striatal axons are seen parallel to dendrites as "woolly fibers" has led to exaggerate the distances along which dendrites and axons are parallel. Striatal axons may in fact simply cross the dendrite and give a single synapse. More frequently the striatal axon curves its course and follow the dendrite forming "parallel contacts" for a rather short distance. The average length of parallel contacts was found to be 55 micrometres with 3 to 10 boutons (synapses). In another type of axonal pattern the afferent axon bifurcates and gives two or more branches, parallel to the dendrite, thus increasing the number of synapses given by one striatal axon. The same axon may reach other parts of the same dendritic arborisation (forming "random cascades") With this pattern, it is more than likely that 1 or even 5 striatal axons are not able to influence (to inhibit) the activity of one pallidal neuron. Certain spatio-temporal conditions would be necessary for this, implying more afferent axons.