Monoclonal antibodies targeted against the immune checkpoint molecules CTLA-4 and PD-1 have recently obtained approval for the treatment of metastatic melanoma and advanced/refractory non small-cell lung cancers. Therefore, their use will not be limited anymore to selected hospitals involved in clinical trials. Indeed, they will be routinely prescribed in many cancer centers across the world. Besides their efficacy profile, these immune targeted agents also generate immune-related adverse events (irAEs). This new family of dysimmune toxicities remains largely unknown to the broad oncology community. Although severe irAEs remain rare (∼10% of cases under monotherapy), they can become life-threatening if not anticipated and managed appropriately. Over the last 5 years, Gustave Roussy has accumulated a significant experience in the prescription of immune checkpoint blockade (ICB) antibodies and the management of their toxicities. Together with the collaboration of Gustave Roussy's network of organ specialists with expertise in irAEs, we propose here some practical guidelines for the oncologist to help in the clinical care of patients under ICB immunotherapy.