We planned to investigate the effect of diltiazem onurine volume, urine sodium (Na+) and potassium (K+) excretion and glomerular filtration rate (GFR). Twenty healthy men, aged between 23 and 36 (mean age: 29 ± 0.87) were examined. A double - blind placebo controlled study was completed by weekly intervals in 3 periods. In each period, first day no drug was given, the second day placebo, the third day diltiazem (30 mg or 60 mg) or placebo was given.In the first 6 hour period following diltiazem 30 or 60 mg administration, increases in GFR (p<0.05), urine volume (p<0.01) and urine Na+ excretion weresignificant (p<0.001), but increase in urine K+ excretion was not significant (p>0.05). In the next 18 hour period, we observed that diltiazem did not affectthe excretion of K+ urine volume and GFR (p> 0.05), but increased the excretion of Na+ (p<0.05).