Single unit recordings were obtained from central vestibular neurons in 3 monkeys during passive head movements. Neurons that discharged in relation to head translation or changes in head orientation, but not eye movement (vestibular-only, N=154), were examined in detail. Neuronal discharge rates were analyzed during four stimulus conditions: sinusoidal head translation in the horizontal plane (0.2-4Hz, 0.2G peak acceleration), static head tilt in the vertical plane (±20 °), oscillatory head tilt (0.5-2Hz), and sinusoidal angular rotation about an earth-vertical axis (0.5 or 1 Hz). Vestibular-only cells were divided into 2 groups based on the regularity of their spontaneous discharge rates (CV*). One group (low sensitivity units) exhibited regular discharge rates (CV* < 0.2), weak discharge modulation during head translation (<25 sp/s/G at f=1 Hz), and persistent discharge rates related to static head tilt (0.68 sp/s/deg of head tilt). The second group (high sensitivity neurons) exhibited irregular discharge rates (CV* > 0.2), strong discharge modulation during head translation (~100 sp/s/G at f=1 Hz), and little or no change in discharge rate during static head tilt (0.32 sp/s/deg). The firing rates of some neurons in both groups were modulated during rotation about an earth-vertical axis (42%), but the modulation was greater for neurons classified as high sensitivity units. Previous reports have described neurons similar to the high sensitivity group; however, the low sensitivity ot tilt neurons have not previously been characterized. Significantly, recent theoretical models have predicted neurons with discharge patterns similar to those of low and high sensitivity neurons.