In 1987 the Central Medical Blood-transfusion Committee of the Netherlands Red Cross decided to modify their definition of 'Rh-negative' as it applied to blood donors. Until then the term Rh-negative had been reserved for donations that grouped as C- and E-negative and failed to react with IgG anti-D by the indirect antiglobulin test (IAT). From June 1987, however, donations were considered to be Rh-negative if they failed to react with two strong anti-D sera. An evaluation is presented over the first one and a half years of working with the new definition, the problems that were encountered and the measures that are taken to guarantee the quality of Rh testing.