– Tebuconazole-d9 is intended for use as an internal standard for the quantification of tebuconazole by GC- or LC-MS. Tebuconazole is a triazole fungicide that is active against both seed and foliar fungi. It inhibits 14α-demethylase isolated from U. maydis and S. bicolor with IC50 values of 0.05 and 0.16 nM, respectively. It inhibits the androgenic effect of the androgen receptor agonist DHT (IC20 = 2.89 µM) and is cytotoxic (EC20 = 38.9 µM) in an MDA-kb2 assay. Tebuconazole (50 and 100 mg/kg per day) administered during gestation reduces testosterone levels and increases testicular levels of progesterone and 17α-hydroxyprogesterone in male rat fetuses. It has a feminizing effect on male pups and a virializing effect on female pups. When administered to rats gestationally through postnatal day 42, tebuconazole (20 and 60 mg/kg per day) leads to cell death of pyramidal cells in the CA3-4 region of the hippocampus and layer V of the cortex concomitant with impairment in learning……