In healthy male subjects there was a positive correlation between plasma uric acid and plasma albumin (r = 0 - 43, P less than 0 - 005, n = 49) when repeated measurements of both variables were used for each subject. Changes in plasma albumin induced by in vivo ultrafiltration were not accompanied by changes in plasma uric acid. The correlation of plasma uric acid with plasma albumin cannot be attributed to protein binding of urate. The two variables are probably related indirectly through a common association with an unknown factor or factors.