The pool of HLA-A, B and C-typed blood donors in Hannover for cell-donation increased from 2162 in 1988 to 2406 in 1989. 1032 blood donors declared their readiness to donate thrombocytes; 667 would like to donate bone marrow, 453 of them have undergone complete HLA-A, B, C and DR-typing. Until August 31, 1989 we looked in our data bank for an HLA-identical bone marrow donor for 84 patients from other transplantation centers and for 19 patients who are being looked after in Hannover and in national and international data banks.