Serum uric acid and 24-hour urine uric acid levels were determined in 47 patients with urolithiasis and in 177 healthy volunteers. The normal volunteers had serum and urinary uric acid levels of 6.0-6.4 mg/dl, 619.4-683.7 mg/day for males and 4.6-4.8 mg/dl, 531.5-589.6 mg/day for females. Uric acid levels in both serum and urine were higher in male volunteers than in female volunteers (p less than 0.05), whereas, among patients the ranges of serum and urinary uric acid levels were not significantly different between males and females (p greater than 0.05). However, the normal distribution of the determined small experimental data, was statistically different and is obviously reliable. Patients with urolithiasis showed significantly higher levels of serum uric acid (8.0 +/- 0.3 mg/dl) than healthy volunteers (5.5 +/- 0.1 mg/dl) (p less than 0.05), but showed no difference in urinary uric acid levels compared with healthy volunteers (p greater than 0.05). The highest number of urolithiasis in both male and female patients fell within the same age range of 41-50 years. The 24-hour urine pH of healthy volunteers showed a range of 5.1-7.0 while the patients with urolithiasis had a pH range of 4.6-7.0. It was also found that 33 per cent of patients had urine pH less than 5.0.