ABSTRACTAmong various fetal and placenta/ function tests, the determination of estriol levels in the urine is an indispensable one. In the study presented herein, the basic and clinical aspects of the ESTROTEC kit method for determining estriol levels in the urine of pregnant women which utilizes the HAIR were examined.Estriol levels determined by the use of this kit were very closely correlated with the levels determined by the chemical assay utilizing Amberlite XAD‐2, while the kit is simple in procedure, does not need any special laboratory equipment and apparatus, and yields its result in a short time. For these reasons, it is of high clinical value as a prospective method for large scale screening of fetal and placenta/ functions.In order to judge with estriol levels fug/ml) in the urine specimens collect randomly at single micturition that fetal placental functions are within normal range, it will be necessary that the levels remain not lower than 16 ugjml (positive reaction in 160 times dilution of urine) in the 37th week of pregnancy and the stage beyond it.Taking into account the fact that there is a limit of estriol levels determined by this method such as an erroneous reading of the reaction in one test tube yields a considerably large error in terms of estriol level, it is necessary to observe the pattern of the levels in the course that follows, and considering that the cases with estriol levels of lower than 16 ugjml in the urine specimens collected randomly at single micturition are in fetal and placental hypofunction, it is important to perform fetal and placental function tests in further detai