The cerebellum is involved in a variety of functions, from motor control to cognition. Given its uniform cytoarchitecture, it is thought that functional diversity arises predominantly from regional differences in afferent and efferent connections. In the first part of this thesis, the microcircuitry of afferent input to a single zone (Cl) in the rat cerebellar cortex was mapped in relation to Purkinje cell phenotype. It was found that afferents from specific parts of the inferior olive are associated with individual bands of Purkinje cells that are either Zebrin positive or negative, and that this connectivity also extends to pontocerebellar projections. In contrast to the detailed knowledge of cerebellar inputs, much less is known about the organisation of cerebellar outputs. Recent tracing studies have highlighted a novel projection from the cerebellar nuclei to the striatum via the thalamus, yet presently there is nothing known about the functional significance of this projection. Thus, the second part of this thesis details the electrophysiological mapping of this pathway, by stimulating the dentate nucleus and recording field potentials and single units in the contralateral striatum in urethane anaesthetised rats. The experiments revealed that a short latency pathway connects the dentate nucleus with the dorsolateral striatum, providing a rapid and secure route for the cerebellum to influence activity within basal ganglia circuits. In the final part of this thesis, two operant behavioural paradigms have been developed as an initial step towards understanding the behavioural significance of interaction between the cerebellum and the basal ganglia. The first is a novel task which seeks to dissociate the respective contributions of the cerebellum and the basal ganglia by using externally-cued versus self-initiated movements. The second involved replication and modification of a habit learning paradigm for use in future studies to investigate the role of the cerebellum in habits.