A notable RHD variability has been observed in Central Argentina's current population attributed to the intermixing of different ethnic groups. The Northwestern region of the country is characterized by a markedly Amerindian genetic contribution. In this sense, the definition of the RHD polymorphism in individuals from this area was lacking. A total of 757 donors from Northwestern Argentina, with D negative C and/or E positive (n = 526), and D variant (n = 231) phenotype defined by standard hemmaglutination tube techniques were genotyped using in-house PCR strategies, commercial SNP arrays and Sanger sequencing. RESULTS Among D negative C and/or E positive samples, RHD null (15.40%) and DEL alleles (3.23%) were identified. One unreported SNP c.1001T>A responsible for a null allele was found. RHD*01N.75 (4.18%) and RHD*DEL43 (2.66%) were the most prevalent variants following RHD*03N.01 (8.75%). The characterization of serologic weak D phenotypes showed that RHD*weak D type 1, 2, and 3 variants were found only in 37.24% of the samples, whereas RHD*weak D type 93 was the most prevalent allele (25.11%). Also, a previously unreported missense variation c.764G>A was identified. A RHD genotyping strategy for patients and donors from Northwestern Argentina must consider the detection of the frequently found RHD*01N.75, RHD*DEL43, and RHD*weak D type 93 variants. Taking into account that RHD*DEL43 has scarcely been found in North Americans and Europeans whereas RHD*01N.75 and RHD*weak D type 93 have never been described in populations other than Argentineans, these RHD variants could be attributed to Native Amerindian genetic influence Ver menos