Metabonomic approaches are believed to be one of the powerful methods for disease diagnosis and assessment of patients' conditions. However, many publications have been providing the evidences of the biases caused by many factors such as diet, physical exercises, environment and individual differences in the clinical researches. For the purpose of ensuring the comparability of metabonomic 1H NMR data from different studies, it is necessary to control those nonexperimental factors in the study design and the data analysis.