The immunological definition of malignant lymphatic cells has already been routinely applied by many laboratories over a number of years. Today it is clear and undisputed that the phenotypic data obtained in that way are often very useful and supporting. The immunological definition of non-lymphoid leukemias is not yet as far advanced. Additional surface markers for the recognition of poorly differentiated non-lymphoid cells are clearly needed. In this paper ten monoclonal antibodies to myeloid surface antigens are described. It is hoped that they are a useful addition to the presently available relatively small panel of well studied myeloid surface markers which are displayed by immature malignant blast cells.