In immunotherapy with T cells genetically modified to express chimeric antigen receptors (CAR), autologous lymphocytes are extracted from the patient, genetically modified to obtain CAR-T cells, and reintroduced into the patient to attack cancer cells. The success of this therapy has been achieved in the area of CD19-positive leukemias and lymphomas, being approved for the treatment of non-Hodgkin's lymphomas, acute lymphoblastic leukemia, and multiple myeloma. CARs are proteins that combine antibody specificity with T-cell cytotoxicity. The most common toxicities associated with therapy were not predicted by preclinical testing and include cytokine release syndrome, neurotoxicity, and cytopenias. These toxicities are usually reversible. One of the main challenges facing the field is the high economic cost that therapy entails, so the search for ways to reduce this cost must be a priority. In addition, other challenges to overcome include the situation that not all patients are supplied with the product and the existence of long waiting times for the start of therapy. The aim of this review is to present the development of the structure of CAR-T cells, the therapies approved to date, the toxicity associated with them, and the advantages and limitations that they present as immunotherapy.