The role of sex hormones on oxalate synthesis by liver, transport by renal cortical mitochondria and urinary excretion was studied in adult male and female Sprague-Dawley rats. Orchiectomy decreased the hepatic synthesis of oxalate whereas ovariectomy increased it by 10 per cent. Castration inhibited oxalate transport by the renal mitochondria uncompetitively in both sexes. Urinary levels of oxalate were unaffected after orchiectomy whereas ovariectomy resulted in an initial elevation in the urinary oxalate levels which returned to control values by 21 days. The results are discussed in light of recent data.