Lateralization of the epileptic process in a group of 152 subjects and the relationship of epilepsy to the lateralization of brain functions was studied in smaller groups of 108 and 56 subjects. A unilateral epileptic process in the temporal limbic structures of the brain is localized in the left half of the brain twice (in 64.5%) to four times (in 80.8%) as often as in the right half. The greater the asymmetry of physiological brain functions--in particular motor and verbally symbolic functions--the more is this tendency pronounced. An epileptic process in temporal limbic structures of the left half of the brain is manifested more often in primarily generalized epileptic seizures with initial sudden and complete loss of consciousness. Episodic spike-and-wave activity, which is the typical electroencephalographic correlate of primarily generalized seizures, or of the thalamocortical aetiopathogenetic component of the epileptic process, is often asymmetrical in amplitude, which in 68.1% of these cases is twice as high over the left hemisphere. An epileptic process in subcortical structures of the right hemisphere impairs physiological asymmetry of emotive facial mimicry (with preponderance of mimic reactions on the left) and in 68.4% of the cases causes atypical preponderance of emotive mimicry in the right half of the face. A unilateral epileptic process in subcortical structures of the left half of the brain has a more favourable course and more hopeful prognosis in 70.4% of the cases, while the course of a right-sided process is worse in 67.6%.