The subthalamic nucleus (STN) has been implicated in motor and nonmotor tasks, and is an effective target of deep brain stimulation for the treatment of Parkinson's disease, likely in part because of the STN's projections outside of the basal ganglia to other brain regions. While there is some evidence of a disynaptic connection between the STN and the cerebellum via the pontine nuclei (PN), how the STN modulates the activity of the neurons in the PN remains unknown. Here we addressed this question using a combination of anatomical tracings, optogenetics, and in vivo electrophysiology in both wild-type (WT) and transgenic mice of both sexes. Approximately half of recorded neurons in the PN, which were located primarily in the medial area, responded with short latency to both single pulses and trains of optogenetic stimulation of channelrhodopsin (ChR2)-expressing STN axons in awake, head-restrained mice. Furthermore, the increase in the activity of PN neurons correlated with the strength of activation of S...