The case histories of 4 patients who developed bone marrow damage after therapy with melphalan are described. In 3 patients bone marrow damage manifested initially as a sideroblastic anaemia which was later followed by acute myeloid leukaemia. The last patient developed a dyserythropoietic anaemia with leucopenia, but thus far there has been no further progression. None of the 4 patients had any haematological abnormality prior to the melphalan therapy. Two were suffering from carcinoma of the breast and 2 had ovarian neoplasms. The fact that melphalan was given as adjuvant therapy in all 4 patients prior to the development of the haematological abnormalities supports the concept that it was of aetiological importance. These findings are in line with a number of reports in the literature in which acute leukaemia has developed in subjects treated for malignant tumours (especially multiple myeloma and ovarian cancer) with melphalan.