Ochratoxin A is a natural contaminant of mouldy food and feed, which is produced by Penicillium and Aspergillus, and is suspected of being one of the etiological agents responsible for Balkan endemic nephropathy and the associated urinary tract tumors. For evaluation of the mutagenicity of ochratoxin A, we performed in vitro chromosome aberration tests using Chinese hamster lung fibroblast cells (CHL cells) and monkey kidney cells (VERO cells), in vivo micronueleus tests using ddY mouse bone marrow cells and somatic mutation and recombination tests (SMART) using Drosophila melanogaster. The results of chromosome aberration tests in CHL cells showed no incidence of increased structural and numerical aberrations regardless of metabolic activation, while in VERO cells treated with 2.0, 1.0, 0.5, 0.3 ug/ml of ochratoxin A showed significant increase of structural aberrations without metabolic activation. Aspartame and-phenylalanine, structural analogs of ochratoxin A, didn't affect the chromosome aberrations induced by ochratoxin A. The in vivo induction of micronucleated polychromatic erythrocytes were measured in bone marrows of ddY mice treated with 10.0, 5.0, 2.5mg/kg/10ml of ochratoxin A through intraperitoneal route once. At 24 and 48 hours after treatment, ochratoxin A didn't induce micronuclei in bone marrows of ddY mice. And at the concentration of 40, 20, 10 ug/ml of ochratoxin A, which was administered by feeding to larvae of Drosophila melanogaster, showed no incidence of increased multiple wing hairs and flares. Summarizing all results, we concluded that ochratoxin A is a kidney cell specific direct genotoxicant.