Genomic variations influencing response to pharmacotherapy of pain are under investigation. Candidate genes such as (opioid)-receptors, transporters and other molecules important for pharmacotherapy are discussed. Drug metabolising enzymes represent a further major target of ongoing research in order to identify associations between an individual's genetic profile and drug response (pharmacogenetics). Polymorphisms of the cytochrome P450 enzymes influence analgesic efficacy of codeine, tramadol and tricyclic antidepressants (CYP2D6). Blood levels of some NSAIDs are dependent on CYP2C9 activity, whereas opioid-receptor polymorphisms are discussed for differences in opioid mediated analgesia and side effects. Pharmacogenetics as a diagnostic tool has the potential to improve patient therapy and care, and it is hoped that pharmacogenetics will individualise drug treatment to a greater extent in the near future.