Embryotoxicity: Aflatoxin B1(AFB1), G1 (AFG1), and Patulin (PA) were investigated in NMRI mice for embryotoxic and teratogenic activity. These three mycotoxins were injected intraperitoneally or given orally on day 12 and 13 of pregnancy. AFB1 (15, 45, and 90 mg/kg ip or 45 mg/kg po) produced a moderate retardation in the fetal development and a dose related increase of cleft palates, wavy ribs, and diaphragm changes. The effects after injection of AFG1 (45 and 90 mg/kg ip) were reduction of fetal weights, increase of diaphragm changes, and malformations of kidneys. PA (1.25, 2.5, and 3.75 mg/kg ip or 3.75 mg/kg po) elevated the rate of cleft palates after 3.75mg/kg. In the dominant lethal assay neither PA (2.5 and 5 mg/kg ip) nor AFB1) (15 and 45 mg/kg ip) increased the frequency of the dominant lethal mutations. Both mycotoxins showed no mutagenic activity in this test system. The capability of AFB1, AFG1, and PA to induce chromosome damages in vivo was tested in the Chinese Hamster by examination of bone marrow cells, each after two oral doses (AFB1: 12.5 and 25 mg/kg; 25 and 50 mg/kg; PA: 10 and 20 mg/kg). The three mycotoxins induced chromosome aberrations in the following order of activity: PA > AFB1 > AFG1.