At American Society of Clinical Oncology’s 2013 meeting, the clinical development of innovative drugs targeting the immune system and progress in biomarker research represented some of the highlights. During recent years, immunomodulatory agents have become a very active field in clinical cancer research. After the successful development of the anti-cytotoxic T-lymphocyte antigen 4 (CTLA4) antibody ipilimumab in melanoma, the “programmed cell death protein 1” pathway is expected to become a cornerstone in several tumor types. One key challenge for anticancer treatment, in general, is the definition of biomarkers and the further individualization of therapy. Progress in molecular phenotyping and in serum proteomics as predictive markers was reported.