Detection of sounds is a fundamental function of the auditory system. While studies of auditory cortex have gained substantial insight into detection performance using animals performing operant conditioning tasks, previous subcortical studies have mostly taken place under anesthesia, in passively listening animals, or have not measured performance at threshold,. These limitations preclude direct comparisons between neuronal responses and behavior. To address this, we simultaneously measured auditory detection performance and single-unit activity in the inferior colliculus (IC) and cochlear nucleus (CN) in macaques. The spontaneous activity and response variability of CN neurons were higher than those observed for IC neurons. Signal detection theoretic methods revealed that the magnitude of responses of IC neurons provided more reliable estimates of psychometric threshold and slope compared to the responses of CN neurons. Correlations between spike count and behavioral response emerged 50-75 ms after sound onset for most IC neurons, but for fewer neurons in the CN. Electrical stimulation of the IC enhanced or degraded detection performance, depending on the response magnitude of the neurons being stimulated. These results highlight the differences between neurometric-psychometric correlations in CN and IC, and have important implications for how subcortical information could be decoded.