To verify prospectively the usefulness of the furosemide-induced natriuresis test in predicting ascites control by medical treatment, 15 stable cirrhotics (9 male) with ascites were studied. Sodium excretion was measured after this test and after volume expansion with saline associated with intravenous infusion of octreotide; 6 months later, response to medical treatment was rated as good (N=9) or poor (N=6). Patients with poor ascites control had lower sodium excretion with the furosemide-induced natriuresis test (median, 88 vs 201 mmol; P < 0.01). Poor control was observed in four of four patients with sodium excretion < or =125 mmol, and good control in six of six patients with sodium excretion >175 mmol (P < 0.002). Volume expansion was followed by limited natriuresis (median, 20 mmol), in inverse relationship with plasma active renin concentration (P < 0.001). In conclusion, long-term ascites control is well predicted by the furosemide-induced natriuresis test.