Abstract: Following pretreatment of adult female rats with contragestational agent 3-(2-ethylphenyl)-5-(3-methoxyphenyl)-1H-1,2,4-triazol(DL111-1T) 20 mg/kg.d for 2 consecutive days, the hepatic microsomal MFO and UDPGT activities were induced to a constant level,being chacacteristic of arylhydrocarbon type of induction. Coincubation of human amnion FL cell with 0.1 μmol/L of DL-111-1T for 24 h produced a 4.5-fold induction of AHH activity of the cell. This inducing ability was 3 times that of PB, but 1/2 that of 3-MC. According to these observations, DL-111-1T may also be considered as a polycyclic arylhydrocarbon type inducer toward human amnion FL cell's MFO which contains mainly of cytochrome P-448. UDS test showed that DL-111-1T itself could not induce UDS of FL cell.