The reaction of Hector Battifora mesothelial epitope-1 (HBME-1) antibody with scattered pronormoblasts in normal bone marrow core biopsy specimens has been reported. This study evaluated the immunohistochemical profile of HBME-1 in a panel of 52 normal, dyserythropoietic and neoplastic marrow samples. We compared the staining property of HBME-1 with that of the commonly used erythroid marker, glycophorin A (CD235a) and in each case, we semi-quantitatively evaluated the HBME-1/CD235a-positive cells ratio. In normal samples, HBME-1 labelled scattered immature erythroid precursors. In dyserythropoietic specimens, HBME-1 stained nucleated erythroid precursors in varying degrees, from pronormoblast through normoblast stages, with the highest intensity in immature forms. Overall, the cellular background of non-erythroid progenitors, erythrocytes and neoplastic cells did not react with HBME-1, except in leukaemia cases with myelodysplasia-related changes. Our study shows that HBME-1 is a useful marker to identify immature erythroid precursors and that an HBME-1/CD235a-positive cells ratio ≥10% is associated with dyserythropoiesis.