When expression of one gene depends on the presence or absence of another gene in an individual, it is known as gene interaction. The interaction of genes at different loci that affect the same character is called epistasis. In genetics, gene-gene interaction is the effect of one gene on a disease modified by another gene or several other genes. Epistasis can be contrasted with dominance, which is an interaction between alleles at the same gene locus. The gene that masks another gene is called epistatic gene, and the gene whose expression is masked is termed as hypostatic gene. Epistasis is also referred to as inter-genic or inter-allelic gene interaction. Gene-gene interaction is a common component of genetic architecture of human complex diseases; however, it is difficult to detect. Pharmacovigilance and Pharmacoepidemiology Journal offer a stage in Pharmacoepidemiology Researches and related subjects. Journal accepts leading forefront original research papers, review manuscripts, case reports and commentary in the field.