Background. In among mycotoxins, secondary metabolites of toxinogenic moulds, ochratoxin A and aflatoxins occupy a prominent pláce. These mycotoxins háve been - as etiologic agents - associated with a wide numbers of acute and chronic human diseases including mycotoxicoses like Balkán endemic nephropathy oř liver cancer. While the risk of acute toxic effects of ochratoxin A and aflatoxin Bt is usually considered to be minimal in the Czech Republic, the situation is different as far as the risk of the latě toxic effects (particularly carcinogenic), which result from a single oř repeated intake of low doses of these mycotoxins from foodstuffs is concerned. Methods and Results. The presence of ochratoxin A and aflatoxins in human environment has been monitored within the program "Monitoring the health statě of the population". As for ochratoxin A, 2206 samples of blood sérum were investigated, 2077 (94 %) of them turned out to be positive (with levels >0,l |xg.l4), the average was 0,28 |xg.r\ the medián was 0,2 ixg.l"1, and the percentile (90 %) was 0,5 |xg.r\ The ochratoxin A levels ranged from 0,1 to 13,7 |xg.r' of sera. The presence of ochratoxin A was also analyzed in 30 samples of human kidneys; 12 samples were positive (with levels >0,l |xg.r'), the average was 0,07 ixg.kg"1, the medián was 0,05 |xg.kg"\ As for aflatoxins, in 1997-1998 the presence of aflatoxin Mj was investigated in 205 samples of human urine; 118 samples (58 %) were positive (with levels >125 pg.l"1 of urine). Conclusions. When calculated to a concentration of creatinine in urine, the average was 391 pg.g"1, the medián was 127 pg.g', and the percentile (90 %) was 585 pg.g'. The aflatoxin Mj levels ranged from 19 to 19 219 pg.g' of creatinine

        Key words: mycotoxins, human exposure, risk assessment, monitoring, biomarkers