This chapter discusses the cholinergic actions of nicotinic and muscarinic receptors (nAChRs and mAChRs) to understand the development and function of auditory cortex (ACx). Neurons in ACx receive synaptic inputs from a much wider range of frequencies than the range that overtly excites the neuron. The synaptic receptive field of a neuron in ACx—produced by integrated thalamocortical and intracortical activity—may be an important target of cholinergic regulation. Cortical plasticity, including reorganization of topographic maps and single cell receptive fields, can involve cholinergic inputs and differential strengthening and weakening of existing synapses. Rapid, transient changes in receptive fields that result from shifting attention may also depend on cholinergic modulation of synaptic strength, given likely cholinergic involvement in mechanisms of attention. The transient expression and function of α 7 nAChRs during development of ACx suggest the existence of a “critical period” of heightened sensitivity to sensory experience, especially given the proximity to the onset of hearing.