The detection of diethylstilboestrol (DES) in urine by thin-layer chromatography The use of synthetic hormones, with both an anabolic and an oestrogenic action, such as diethylstilboestrol (trassdc,a'-diethyl-4,4'-stilbenediol) has gained in popularity during the last years, especially in connection with the fattening of calves and poultry. The fact that these compounds belong to the so-called biologically highly active compounds and the presumptions expressed in literature that they possess carcinogenic or cancer-stimulating activity made several governments decide to prohibit the use of compounds with a hormonal activity for other than therapeutic purposes. Hence the detection of DES is of special interest.In The Netherlands DRYER'S~ bromimetric method and BANES AND UM-BERGER'S~~~ U.V.-irradiation method, both in a modification of Huzs IN 'T VELD*, are used for quantitative determination of DES. Besides these, need was felt for a simple specific identification method. Thin-layer chromatography turned out to be suitable for this purpose.The use of paper chromatography for the detection of DES has been described a few times. In accordance with the chemical character of DES a method based on so-called "reversed-phase" chromatography 3-s had to be developed. In view of the time-consuming character of this technique it is surprising that more attention has not --* L. G. HUIS IN