The frequency-following response (FFR) is a sustained auditory-evoked potential that reflects the phase locking of neurons in the auditory brainstem to periodicities in the waveform of a sound. Studies have shown that short-term auditory training can improve the robustness and/or accuracy of this phase locking. FFR plasticity has been investigated using training tasks that are thought to involve some form of auditory temporal coding, including fundamental-frequency discrimination training, training to identify Mandarin lexical tones, and training to identify speech in noise. The results of these studies have shown that improvements in the trained task are often accompanied by FFR plasticity. This suggests that subcortical auditory processing is not hardwired but can be modified by training even in adulthood. The FFR has also been shown to change following auditory-cognitive training protocols in special populations of listeners who may have subcortical auditory processing deficits, such as children with language-based learning disabilities, elderly listeners, and listeners with sensorineural hearing loss. The results of these studies provide promising evidence that subcortical auditory plasticity could be harnessed to ameliorate auditory processing deficits. It has been hypothesized that this learning-induced subcortical plasticity may be guided by efferent cortical feedback; however, the mechanisms of FFR plasticity remain largely unclear.