The clinical significance of hypouricemia in hospitalized patients was studied retrospectively and prospectively. Two thousand two hundred patients routinely screened for serum uric acid were reviewed: 88 (4%) had serum uric acid levels below 2.5 mg/dl and 23 (1%) below 2 mg/dl. We found that 32 (36.4%) patients with serum uric acid below 2.5 mg/dl were patients treated with forced diuresis. Thereafter, to confirm the importance of perfusions in the evaluation of serum uric acid levels, 20 suicide-attempt patients and 7 patients with renal colic all treated with forced diuresis, were prospectively studied. Our results show that perfusions significantly increased the fractional excretion of uric acid that was responsible for the observed decrease of serum uric acid level.