The development of unrelated bone marrow donor search (UMDS) was analyzed in a retrospective single-center study covering the period from 1991 to 1994. The data files of the 285 enrolled UMDS patients were evaluated for the patients' underlying disease, HLA phenotype frequency, year of search start, UMDS duration/outcome, and the origin of identified donors. Within 3 months after UMDS start, a donor was found in 5%, 10%, 19%, and 49% of the searches started in 1991 (n = 57), 1992 (n = 73), 1993 (n = 77), and 1994 (n = 78, until September), respectively. The total UMDS success rate increased from 53% (1991 group) to 67% (1994 group), with 5% and 54%, respectively, of the accepted donors being supplied by German registries. Thus, the current UMDS procedure provides a suitable donor for the majority of the patients lacking a related donor, and the majority of the donors are now facilitated by national donor centers.