The intermediate nucleus of the lateral lemniscus (INLL) is a major source of projections to the inferior colliculus (IC), the auditory midbrain center where multiple inputs converge to create neurons selective for specific temporal features or patterns of sound. However, little is known about how it processes auditory information or how it contributes to integrative processes at the IC. The INLL itself must perform some form of integration because it receives multiple inputs including excitatory projections from the cochlear nucleus and inhibitory projections from the medial nucleus of the trapezoid body. To address the question of what role inhibitory synaptic inputs play in the INLL of the big brown bat (Eptesicus fuscus), we recorded sound-evoked responses of single neurons in INLL and iontophoretically applied bicuculline to block GABA_A receptors or strychnine to block glycine receptors. Neither bicuculline nor strychnine had a consistent effect on response latency or frequency response areas. Bicuculline led to increased spike counts and response durations in most units, suggesting that GABAergic input suppressed the late part of INLL neurons responses and provided some gain control. Strychnine reduced the responses of a subpopulation of units so that sustained discharge patterns were limited to one or a few spikes at stimulus onset. INLL is the first area where reduced responsiveness has been seen in vivo while blocking glycine. In vitro studies in the medial nucleus of the trapezoid body suggest that glycines facilitatory effect may be due to presynaptic action.