Although patients suffering from syndrome of inappropriate ADH secretion (SIADH) have normal BP levels (11) and some authors have found no differences in plasma AVP between normotensive and hypertensive subjects (12), others have shown that individuals with hypertension have significantly higher levels of urinary and circulating AVP, which positively correlate with DBP (7, 8, 14, 27). This evidence concerns the gene AVP and hypertensive disorder.