Seventy-two IgG anti-D Mabs were studied by indirect immunofluorescence and flow cytometry (FCM) with R1r, rr and various D variant phenotype red blood cells (RBCs) (DIIIb,DVI,DVII,Rh33 and uncategorized variant ISBT number 48). The results were compared with those obtained by indirect antiglobulin test (IAT).