A high degree of synchrony can exist in the timing of complex spikes within individual Purkinje cells located in the same parasagitally aligned strip or zone of cerebellar cortex. However, it is not known whether the simple spike activity of the same neurones can also occur synchronously and whether any observed synchrony can be modulated by peripheral inputs. Experiments in the present study were designed to explore this and related questions using multiple single unit recording techniques. In particular, we aimed to assess the degree of correlation in simple spike and complex spike firing patterns of simultaneously recorded Purkinje cells located within the same cerebellar cortical zone as compared to pairs of cells recorded within different zones. Adult Wistar rats were anaesthetised with ketamine (100mg/kg) and xylazine (5mg/kg i.p.). Percutaneous electrical stimulation of the ipsilateral forelimb and contralateral face region was used to evoke field potentials on the surface of the cerebellum in order to locate the A2 and C1 cerebellar cortical zones in the paramedian lobule. The zonal electrophysiology was used to guide the insertion of four independently controlled glass insulated tungsten microelectrodes into the cortex. Up to four Purkinje cells were recorded simultaneously within the two neighbouring zones. The simple spikes and complex spikes generated by individual Purkinje cells were discriminated independently and peri-stimulus time histograms were constructed for forelimb and face stimulation. Correlation coefficients were calculated between the occurrence of complex spikes and also between the occurrence of simple spikes for the same pairs of Purkinje cells. Preliminary findings indicate that correlation coefficients are larger in Purkinje cell pairs that are located in the same zone compared to pairs that are located in different zones. Purkinje cell pairs exhibiting a high correlation in complex spike activity exhibited a transient increase in simple spike synchrony following peripheral stimulation. The increase in simple spike correlation was not observed in the spontaneous simple spike activity of the same Purkinje cells, nor in Purkinje cell pairs that did not exhibit a high level of complex spike synchrony. These initial findings suggest that Purkinje cells with a common climbing fibre input can also have a common mossy fibre input, but that the latter is only apparent following peripheral stimulation.