Extracellular recordings were made from afferents to the Purkinje cells of the flocculus of monkeys either spontaneously making saccadic eye movements (saccades) or trained to fixate a small visual target projected on a tangent screen. In the trained monkeys, saccades of known magnitude and direction were induced by changing the position of the fixation target. 2. Among a population of 108 units, eight were climbing fibres, seventy-one were mossy fibres, and twenty-nine were non-Purkinje cells. Based on their discharge patterns the latter two groups of units were categorized into one of four classes. 3. Long-lead burst units (twenty-two units) exhibited saccade-related discharges substantially before saccade onset (average: 113 msec). Most of these (twenty units) discharged for saccades in a particular direction, while the remainder exhibited discharges for saccades in all directions. All units were essentially silent between saccades. 4. Burst units (twenty-seven units) started discharging slightly before saccades (average: 6.9 msec). Discharges were associated with saccades in all directions (sixteen units) or in preferred directions (eleven units) and were not observed during periods of fixation. 5. Burst-tonic units (twenty-two units) were characterized by saccade-related burst and position-related intersaccadic tonic activity. 6. Tonic units (thirty-seven units) exhibited position-related tonic activity. The position-related activity in both burst-tonic and tonic units was observed only for fixation points within a specified region. The units were silent for fixation positions outside this region of preferred fixation.
