"Individualized therapy strategies" involve strategies that allow treatment to be guided by patient-specific conditions. For this, robust biomarkers are needed. Examples of biomarker-guided therapies already in use are the treatment of insulin-dependent diabetes (biomarker: blood glucose level) or the treatment of hypertension (biomarker: blood pressure). By contrast, most immunomodulatory therapies are given according to the patient's body weight or the patient's drug blood level rather than according to biomarkers indicating the patient's state of the immune system. Herein we report on new biomarkerguided studies in the immunosuppressive treatment of transplant patients and patients with autoimmune disease and we discuss its benefits and pitfalls.