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......