Recently developed brain stimulation techniques such as transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) use electromagnetic principles to noninvasively alter brain activity, with the precise effects varying as a function of stimulus intensity, frequency and duration, as well as the target location. The ability to manipulate brain activity in a temporally and spatially specific manner has helped delineate the time-varying contributions of various brain regions to normal cortical function. When combined with other brain imaging technologies such as MRI, PET and EEG, these brain stimulation techniques can also provide additional insights into the network dynamics and functional connectivity of different brain regions. Such studies have played an important role in advancing our understanding of the processes that underlie normal brain functions such as sleep and language, and the alterations that occur in pathological conditions such as depression. Furthermore, these techniques have also been used to study the brain’s response to injury, such as in motor recovery after ischemic stroke. Because brain stimulation techniques can also be used to noninvasively produce potentially long-lasting, predictable changes in cortical activity, their utility in the treatment of various neuropsychiatric disorders is also being actively explored, with some encouraging results. Consequently, brain stimulation techniques are promising and important new tools in the understanding of cortical function and treatment of brain pathology.