Just about one and one-half centuries ago, Paul Broca identified the posterior third left frontal convolution of the human brain as a critical area for speech production. Although years of cerebrovascular accident localization studies partially confirmed Broca's claim, recent years have seen a clarification and expansion of the role Broca's area plays in serial processing of language and speech as well as a probable role in nonlinguistic processing. This article will review some of the more recent anatomical and physiological research, including lesion studies, imaging research, and interoperative electrocortical stimulation studies. The article will summarize the research on the role of the human inferior frontal gyrus in lexical, phonologic, and grammatical production, the so-called "mirror mechanism" and other aspects of cognitive processing and motor execution.