AIM: To explore the role of endogenous ouabain (EO) in the development of hypertension and its secretion character in 1k1c hypertensive rats(HR). METHODS: EO contents of plasma and tissues in 1k1c HR were detected by ELISA. The relationships between plasma and tissues ouabain and blood pressure were analyzed. RESULTS: EO contents of plasma, heart, kidney, adrenal gland, pituitary and hypothalamus in lklc HR were significantly higher than those of normal rats, especially in the adrenal gland and hypothalamus. EO contents of serum, kidney and hypothalamus were correlated with blood pressure. CONCLUSIONS: EO might play an important role in the development of hypertension in 1k1c hypertensive rats. Adrenal gland might be the major source of EO.