A simple, fast, and specific HPLC-method to estimate retinol (vitamin A) in serum is reported. In the presence of small amounts of acetonitrile retinol is extracted quantitatively with n-hexane from serum. Neither the use of an internal standard nor evaporation to concentrate the extract is necessary. The HPLC-method avoids interferences of substances like phytofluenes, carotinoids or retinyl palmitate which is present in serum to a fraction of about 2-5%. The HPLC-method was applied to healthy adults and healthy children. The method allows about 100 determinations per day and operator.