Objective: Biological variation-(BV) data of analytes have been used to evaluate the significant changes in serial results of healthy individuals in clinical laboratories. The aim of this study was to calculate within-(CVw)-(within-individual BV) and between-individual (CVg)-BV, index of individuality,and RCV of urine Melatonin analyte in patients with Chronic Hepatitis B(CHB). Material and Methods: 20-CHB patients and 20 healthy individuals as control were involved in this study. Index of individuality and reference change value were calculated from within-subject and between-subject variations. Melatonin levels in human urines was measured with commercial a kit by-ELISA.ANOVA test was used to calculate the variations. Results: Melatonin were significantly higher in patients with CHB compared to healthy subjects. Also,RCV of Melatonin analyte in CHB patients was relatively higher, because of high within-subject variation,resulting in a higher RCV. Conclusion: RCV concept for predicting the clinical status in CHB patients represents an optimization of laboratory reporting and could be a valuable tool for clinical decision.