Salicylamide glucuronide (SAMG) in 0-6 and 6-12 hours-urine specimens was determined after oral administration of salicylamide in 7 normal volunteers (NV), in 51 cases of various liver diseases and hyperbilirubinemias, and in 19 cases after drug administration, to predict the in vivo drug metabolism in man and its change by drugs. Maximal glucuronide formation was obtained by 1.0 g of salicylamide administered to NV; thus, this dosage was used in the present study. SAMG as percent of total salicylamide, the percent of SAMG, from 0-6 hours-urine specimens was high and constant in NV (71.3 +/- 8.3 (Mean +/- S.D.)). 0-0.08% of the total salicylamide was confirmed as free salicylamide in 0-12 hours-urine specimens of NV. The percent of SAMG of 0-6 hours-urine specimens was 57.2 +/- 8.6 in acute hepatitis, 66.6 +/- 10.9 in chronic hepatitis, and 48.6 +/- 10.7 in liver cirrhosis (mean +/- S.D.). Free salicylamide increased slightly in liver diseases. Serum bilirubin levels tended to be inversely correlated with the percent of SAMG. In most cases of Gilbert's syndrome, the percent of SAMG remained at a normal level. The percent of SAMG in cases with unconjugated hyperbilirubinemias of other geneses were almost within normal limits. Bucolome and phenobarbital increased the percent of SAMG in patients with various liver diseases. After rifampicin or phenytoin administration, the percent of SAMG of the patients with lung tuberculosis or epilepsy did not surpass that of NV.