In this section, it is demonstrated how metabonomics can be used for monitoring specific biomarkers. Thereby no special assay for the biomarker has to be developed but the common routine measurement of metabonomics can be used. If a signal of the biomarker is not overlaid by other signal, the relative concentration of this biomarker can be directly assessed on the basis of the integral of this signal. The possibility of monitoring specific biomarkers is shown using the example of phospholipidosis.