OBJECTIVE: We examined serum in patients of liver injury to explore the possible clinical application of abnormal micrometabolites as a marker of liver injury and severity in cases of traumatic liver damage. METHODS: Serum were screened by proton nuclear magnetic resonance spectroscopy in 96 patients with varying degree of liver injury and compared with concentrations in healthy control volunteers. RESULTS: Large quantities of phenylalanine and tyrosine were detected by spectroscopic analysis in patients with liver injury but not in those without liver injury (P < 0.001). Proton nuclear magnetic resonance spectroscopy revealed two unique amino acids, phenylalanine and tyrosine, in the sera of the subjects with liver injury, irrespective of the extent and type of injury gauged by radiology or laparotomy. Phenylalanine spectrum was obtained in all 84 patients with liver injury (100% sensitivity) whereas tyrosine spectrum was present in 83 out of 84 patients (98.8% sensitivity) suggesting that these amino acids were specifically released in the patients of liver injury. Significant correlations were observed between phenylalanine and tyrosine concentrations and total bilirubin levels and albumin levels. Serum phenylalanine and tyrosine concentrations correlated well with imaging and laparotomy findings of liver injury. CONCLUSION: Phenylanaline and tyrosine appear to be specific and new markers of liver injury.