['Intestinal mucosal barrier injury (MBI), resulting from myeloablative conditioning for haematopoietic stem-cell transplantation (HSCT), is an important cause of morbidity. Despite its frequency, recognition presents a challenge, while the aetiology needs still to be unravelled. The relationship between enterocyte mass and enterocyte loss was explored by examining citrulline serum levels and by assessing circulating intestinal fatty acid-binding protein (I-FABP) and ileal bile acid-binding protein (I-BABP), proteins released by dying mature enterocytes.', 'Thirty-four adult patients with haematological malignancy received allogeneic HSCT (HSCT day 0) 12 days after being given idarubicin, cyclophosphamide and total body irradiation as myeloablative conditioning, a regimen known to induce oral and intestinal MBI. Serum levels of citrulline, I-FABP and I-BABP were measured on HSCT days -12, -6, 0, +7, +14 and +21.', 'Myeloablative conditioning resulted in a significant decrease in serum citrulline with the nadir on HSCT day +7; thereafter, levels rose gradually. Simultaneously, a significant decrease in I-FABP and I-BABP levels occurred from the day of transplant until day +14.'] Is loss of enterocyte mass accompanied by diminished turnover of enterocytes after myeloablative therapy in haematopoietic stem-cell transplant recipients?