Ochratoxin A (OTA) is a mycotoxin food and feed-contaminant known to induce nephro and hepatotoxicity in human and animal, and related to human Balkan Endemic Nephropathy. However, haematological troubles are also observed in case of acute OTA intoxication. These disorders observed in animals emphasise the necessity to determine if OTA exposure induce damage to haematopoietic system in human. The effect on haematopoiesis has been evaluated using in vitro clonogenic assays of the three lineages i.e., platelet, red and white blood cell progenitors. Human erythroblastic and granulomonocytic progenitor proliferation is decreased in the presence of 10(2) microM OTA. Platelet progenitors were destroyed at 10(2) microM OTA. For the lowest concentrations haematopoietic progenitor proliferation is not affected by OTA. Comparison with other mycotoxins known to be myelotoxic shows that OTA is less myelotoxic than trichothecenes.