The traditional view of the organisation of the basal ganglia is that cortical information is processed within the striatum, transmitted through the so-called direct and indirect pathways to the output nuclei of the basal ganglia; the basal ganglia then influence behaviour by the output nuclei project to thalamus us and then back to cortex or to sub-cortical structures involved in movement. However it has long been known that another major excitatory input to the basal ganglia arises in the thalamus, principally, but not exclusively, the intralaminar nuclei. We have carried out a series of experiments to study the thalamic innervation of the basal ganglia (mainly the thalamostriatal projection) using a multiplicity of approaches. In vivo extracellular recording and juxtacellular labelling in anaesthetised rats reveals that neurons in different sub-nuclei of the thalamus have remarkably different morphological and physiological properties and give rise to different connections in the striatum (Lacey et al., 2007). The use of molecular markers of the of the corticostriatal and thalamostriatal pathways, vesicular glutamate transporters type 1 and type 2 respectively (VGluT1 & VGluT2), have revealed key aspects of the involvement of thalamostriatal synapses in striatal circuitry. 1) The thalamostriatal pathway gives rise to a similar number of synapses in the striatum as does the corticostriatal pathway (Lacey et al., 2005). 2) Thalamostriatal synapses have the same spatial relationship with dopaminergic afferents to the striatum as do corticostriatal synapses. This implies that thalamostriatal synapses are likely to be modulated, like corticostriatal synapse, by released dopamine (Moss and Bolam, 2008). 3) Both the corticostriatal pathway and thalamostriatal pathway innervate striatal projection neurons giving rise to the direct and indirect pathways to similar degrees (Doig et al., submitted). The neuronal networks of the basal ganglia are organized in such a way that the excitatory inputs to the striatum ‘select’ which individual striatal projection neurons, or groups of neurons, are depolarized from the relatively hyperpolarized resting state. With sufficient convergent excitatory input, and appropriate modulatory influence of released dopamine, the ‘selected’ population of projection neurons will fire action potentials, and it is this that underlies basal ganglia-associated behavior. The present findings, together with those of others, suggest that although the thalamostriatal pathway carries different functional information from that of the corticostriatal pathway, and encodes it in an heterogeneous manner (Lacey et al., 2007), it is likely to be equally involved in the ‘selection’ of individual or populations of striatal projection neurons.