A Monoclonal Antibody Program was launched at the National Institute of Oncology and Radiobiology (INOR) in Cuba in 1985. Eleven MAbs have been obtained which recognize different leukocyte antigens. Four MAbs a series of reagents raised against different types of cytokeratins, carcino-embryonic antigen and the membrane receptor for Epidermal Growth Factor. These MAbs are especially useful in immunohistochemistry for the study of human tumours, leukemias and lymphomas. Three ultramicro-ELISA systems have being deviced using MAbs. First trials are being made with radioactive MAbs for immunoscintigraphy. The use of anti T-cell MAbs for the prevention of rejection crisis in patients receiving organ transplantation and for the treatment of patient with cutaneous T-cell lymphoma is still mostly a matter for research.