Unrelated donor (UD) bone marrow transplantation (BMT) represents an attractive option for patients with haematological, oncological or genetic diseases lacking a compatible familiar donor. Between September 1988 and December 1997 the search of a donor has been activated for 1724 patients in Italy. Until May 1998, 413 BMT from UD have been performed in 28 different authorized italian centres. Forty out of these patients were affected by genetic diseases apart from SCID (severe combined immunodeficiency). Sixty-month disease free survival (DFS) of this group was 62%. Seventy-four out of 215 children with acute lymphoblastic leukemia (ALL) for whom a donor search was started underwent a BMT. Six year DFS was 25%. Fifty-nine out of 379 patients with chronic myeloid leukemia (CML) for whom a donor search was activated underwent BMT. Forty-eight month DFS was 41.5%. Inborn errors curable with BMT, relapsed ALL and CML represent an absolute indication for UD BMT. In these cases donor search should be activated yearly.