The presence of ochratoxin A (OTA) in human blood has been reported for many countries, especially in Europe. However, so far no report exists concerning such a presence in Argentina. The aim of this study was to assess OTA concentration in human plasma in two different areas of Buenos Aires province. OTA was determined by high-performance liquid chromatography (HPLC) in 199 plasma samples from blood donors in Mar del Plata and 236 from General Rodriguez. Solid-phase extraction with Bakerbond C-18 cartridge and a final purification with Ochraprep immunoaffinity columns was employed. The limit of quantification of ochratoxin A was 0.019ngml(-1) and the confirmation of OTA was by formation of ochratoxin A methyl ester. The results showed that 63.8% of human plasma samples from Mar del Plata and 62.3% from General Rodriguez were positive for OTA, with Winsorized means of 0.15 and 0.43ngml(-1), respectively. It is important to continue the research to detect the foods responsible of the presence of OTA in plasma.