Neuronal development is a progressive series of constructive and reductive events including division of progenitors, their accretion at specific locations, differentiation into neuronal and glial subtypes, and circuit refinement. The final goal is to establish adaptive neuronal circuits controlling the behavior of the organism. The complex architecture of the adult auditory cortex (AC) is thus the consequence of many developmental processes taking place prenatally and postnatally. The end of the developmental period is traditionally defined by sexual maturity; however, substantial adaptations in cortical circuitry continue throughout life. We identify some rules applicable to cortical development in general and to AC in particular, concentrating on the species most common in hearing research. We build on comparative reviews on the structural and functional development of the auditory system (Payne 1992; Cant 1998; Sanes and Walsh 1998; Romand 1997; Yan 2003). We also consider studies on the AC structural and functional plasticity during development. Studies on adult plasticity are beyond the scope of this analysis.