Rare blood is generally defined as one that occurs at a frequency of 1:100˜1000 individuals or less, and it is sometimes difficult to provide such blood types to patients because of their rarities. The Japanese Red Cross (JRC) Society lists 46 rare blood phenotypes that are divided into two categories. The rare blood types listed in Category I occur much less frequently than those listed in Category II. We screen for rare blood cells using monoclonal antibodies (MoAbs). Since 1987, our blood centre has established 93 MoAbs (32 human and 61 murine) and has provided them to the other blood centres. Many of IgG MoAbs are available on the machine by saline or bromelin method by cross-linking with anti-human or anti-mouse IgG. Thus, more than 10 000 donors with rare blood phenotypes (Category I, 748; Category II, 9314) are registered in Japan. We freeze rare blood, particularly Category I types. Since 1977, a total of 576 units of rare blood with phenotypes Di(b−), D−−, Jr(a−), Ko and Lan-, etc. have been supplied to 23 international countries. Thus, the JRC contributes to the International Panel of Donors of Rare Blood Type (IDP) which is maintained by the International Blood Group Reference Laboratory (IBGRL) in Bristol, UK. The IDP provides information on the location of rare blood donors when they cannot be found in their respective countries. We also joined the ISBT Working Party on Rare Donors which handles all matters related to rare blood. Our rare blood donor programme is successful because of international co-operation.