Much progress has been made in omics research following completion of the Human Genome Project. This comprehensive analysis produced a new discipline (i.e., bioinformatics), and its findings contributed to the clinical practice of anesthesiology. Genomes of patients show genetic variations and may predict the sensitivity to anesthetics and analgesics, incidence of adverse effects, and intensity of postsurgical pain. Changes in the transcriptomes of patients may also reflect anesthesia-related expression profiles of various types of neurons in the brain, and information on such changes may contribute to molecular targeted therapy in anesthetized patients. In addition, novel epigenome research may explain why environments change the phenotypes of clinical anesthesia. We currently hypothesize that female gender is associated with DNA methylation in pain-related and vomiting-related gene promoter regions at the genome-wide level and that epigenetic mechanisms are involved in gender differences in anesthesia practice.