The neurotransmitter dopamine is implicated in a wide range of brain processes and dysfunction of the dopamine systems leads to severe neurological and psychiatric problems. Dopaminergic (DA) neurons respond in a highly stereotyped fashion to a wide range of sensory stimuli with a short latency (<100 ms), short duration (~100 ms) burst of action potentials (reviewed by Redgrave & Gurney, 2006). However, the precise function of the dopamine signal is still being hotly debated. Our approach to this problem has been to study the properties of the structures which supply information to the dopamine systems, in particular those which provide sensory information. Initial studies in the anaesthetised rat using extracellular recording in vivo demonstrated that DA neurons are unresponsive to visual stimuli at baseline, but respond phasically to these stimuli following disinhibition of the midbrain superior colliculus (but not the visual cortex), suggesting that this comparatively primitive structure is the primary if not exclusive provider of visual information to DA neurons: a conclusion which challenges the widespread belief that DA neurons signal aspects of a high level construct, namely reward (Dommett et al, 2005). This conclusion was reinforced by the discovery, using anterograde and retrograde tract tracing techniques, of a direct projection from the colliculus to DA neurons in the midbrain, referred to as the tectonigral projection (Comoli et al. 2003). However, recent in vivo electrophysiological evidence in the monkey suggests that the short latency dopamine response to sensory stimuli has a short and a longer latency component, and that the latter may have a more highly processed (evaluated) content. Furthermore, evidence suggests that the origin of the longer latency component of the dopamine signal may be the neocortex, acting via the superior colliculus. Our recent retrograde tract tracing experiments in the rat show that widespread areas of the neocortex project to the superior colliculus, and extracellular electrophysiological experiments show that electrical stimulation of the visual and somatosensory cortices in the anaesthetised rat produces short latency phasic responses in DA neurons, in many cases only when the colliculus is disinhibited. Cells responding in the absence of collicular disinhibition show response attenuation when collicular inhibition is increased. Initial observations suggest that subcortical and cortical sensory information is conveyed to DA neurons by the same collicular cells, which are not modality specific. Hence, the colliculus appears to be a final common pathway by which certain classes of sensory information reaches DA neurons. Given that both components of the dopamine response to sensory stimuli in the monkey have a pre-saccadic latency (>200 ms), neither component of the signal is likely to convey a full evaluation of the stimulus. In very rare contexts in which stimuli are highly familiar (e.g. after overtraining), the cortex may provide sufficient pre-saccadic processing to determine value. However, the function of this value component of the DA signal is unclear, given that the activity of DA neurons does not appear to encode value more generally, since with unfamiliar stimuli requiring foveation for evaluation, post-saccadic value related responses have not been demonstrated in DA neurons.