The content of indoxyl-beta-D-glucuronide, which has been found in patients' plasma as a new indicator of renal failure, logarithmically correlated with that of 3-indoxyl sulfate (indican) in the plasma of hemodialysis patients, showing another weak correlation with beta(2)-microglobulin content. The content ratio of indoxyl-beta-D-glucuronide to 3-indoxyl sulfate (IG/IS) gradually increased depending on the duration of hemodialysis treatment. Indoxyl-beta-D-glucuronide could be easily dialyzed in the hemodialysis treatment, in contrast to hardly dialyzable 3-indoxyl sulfate which bound to plasma proteins. Therefore, glucuronide conjugation in indole excretion is favorable for hemodialysis patients in that it eliminates indoxyl compounds in blood by hemodialysis.