Genetic studies of the epilepsies involve two main aspects: detailed gathering of data and data analysis. The contribution of genetics to nosology and classification of the epilepsies should be carefully considered. If genetic criteria were prominent, epilepsy syndromes having heterogeneous clinical expressions would be classified within the same category and homogeneous syndromes caused by different genetic mechanisms would fall in different subcategories. The idiopathic generalized epilepsies constitute a group of syndromes characterized by absence seizures, myoclonus, and generalized tonic-clonic seizures. Chromosomal abnormalities are relatively common genetically determined conditions that increase the risk of epilepsy. Ethical and societal considerations are important in establishing guidelines for both genetic counseling and genetic research in the epilepsies. Standard karyotype and high-resolution chromosome analysis, fluorescent in situ hybridization (FISH), molecular karyotyping with array comparative genomic hybridization, multiple ligation-probe amplification (MLPA) and single-nucleotide polymorphism arrays (SNPs) are the standard cytogenetic and molecular techniques for diagnosis.