Since 1956 when Cartwright (Yt) was recognized as a new erythrocyte antigenic system, numerous studies about anti-Yta and anti-Ytb antibodies have been published. A number of these studies described the laboratory techniques utilized in antibody identification, while others investigated the clinical importance of anti-Yta, giving variable results. However, most authors agreed upon the homogeneity of expression in this antigenic system. In our study we have described a case regarding 1 Yt(a+) patient with anti-Yta antibody. Family studies indicated inheritance of a variant/variant expression of the Yta antigen from the father.