Transcranial magnetic stimulation allows a non-invasive and painless stimulation of the human brain and cranial nerves. The method is in use since 1985. Transcranial magnetic stimulation can use single stimuli, pairs of stimuli separated by different intervals (to the same or to several brain areas), or trains of repetitive stimuli at various frequencies. Single stimuli give rise to motor evoked potentials that have clinical use and serve diagnostic and prognostic purposes. Repetitive transcranial magnetic stimulation can modify excitability of cerebral cortex. Repetitive transcranial magnetic stimulation has opened a new field of investigation of the neural circuitry, and is developing into a therapeutic tool. This general review considers basic principles of transcranial magnetic stimulation, discusses methodological aspects and techniques, and analyses their utility in clinical practice.