1. DOCA and 9 alpha-fludrocortisone were given to mice on a high-sodium diet for periods of up to 20 weeks, resulting in decreases in plasma renin concentration, renal renin concentration and renal renin mRNA with both treatments. 2. Plasma renin concentration was suppressed prior to suppression of renin mRNA and renal renin levels, indicating that suppression of synthesis and secretion of renin occur separately. 3. The decrease in renal renin concentration that occurred with DOCA was greater and more rapid than the decrease that occurred with 9 alpha-fludrocortisone, suggesting that DOCA caused intra-renal breakdown of renin. 4. When DOCA was given to mice on a low-sodium diet, plasma renin concentration and renal renin concentration increased, indicating that the effects of DOCA on renin levels were dependent on dietary sodium. 5. Renin secretion and synthesis appeared to be controlled by different mechanisms and sodium balance has an important effect on both processes.