We studied the mechanisms leading to derangement of aldosterone secretion in cirrhosis. The circadian patterns of plasma renin activity (PRA), aldosterone, cortisol, sodium, and potassium were studied in 16 nonazotemic cirrhotics (group 1 without ascites, 7 cases; group 2 with ascites, 9 cases) and 7 healthy controls. Group 1 did not differ from controls in aldosterone, sodium, and potassium mean daily levels (mesors), but had reduced PRA mesor (p less than 0.05). Moreover, minor derangements in circadian patterns of PRA, aldosterone, and potassium were also found. Group 2 not only showed an increased mesor of PRA (p less than 0.05), aldosterone (p less than 0.001), and reduced sodium (p less than 0.005), but also achronia in daily fluctuations of PRA, aldosterone, and potassium. In all groups the mesors of PRA and aldosterone were correlated (r greater than or equal to 0.82; p less than 0.01 or less), but the regression line slopes of patients were steeper than those of controls (group 1, p less than 0.05; group 2, p less than 0.01). Moreover, although in controls and some group 1 patients aldosterone paralleled cortisol rhythmicity, most group 2 patients had aldosterone daily patterns correlated with those of PRA. Finally, no relationships between plasma potassium and aldosterone concentrations were found in patients, whereas they were strictly related in controls. These results suggest that the renin-angiotensin system is the prevalent determinant of aldosterone secretion in cirrhosis.