A so called individualized or personalized medicine is currently stimulating peculiar attention. The terms promise better, i.e. more successful, medical treatment with fewer side effects for the future. The present article discusses the biologic concept underlying the terms as well as the promises connected with it and places the terms into the broader context of diagnostic methods. It is pointed out that an assessment of methods called individualized medicine can and should be carried out in adherence to the same methodological principles as they apply to the assessment of other diagnostic tests. Even individualized medicine needs to be subjected to the standard evaluation and review procedures of evidence based medicine.