Abstract Monoclonal gammopathies (MG) are a group of clinical entities characterized by the clonal expansion of monoclonal immunoglobulin (M-protein) secreting plasma cells (PC). This document presents the consensus recommendations of the Spanish Society of Laboratory Medicine (SEQCML) and the Spanish Society of Hematology and Hemotherapy (SEHH) for the study of MG. The recommendations were established based on scientific evidence and the opinion of experts in MG from the clinical laboratory and clinical hematology fields. Recommendations are proposed for the diagnosis of MG and for patient follow-up according to the type of MG and whether or not the patient is undergoing treatment, and to monitor the disease stability, response to therapy and disease progression. With respect to the diagnosis, we describe the most recent criteria and classification established by the International Myeloma Working Group (IMWG) for multiple myeloma (MM), smoldering MM, monoclonal gammopathy of undermined significance (MGUS) and other related entities. Indications are given about the analytical requirements and application of the different serum and urine laboratory tests (study, detection, identification and measurement of M-protein) and the bone marrow study. Recommendations on the clinical laboratory results report model are established to harmonize and ensure that all relevant information is available, including its content, expression, and interpretive comments.