SummaryWhen one wishes to measure with accuracy theœstrogenic activity on vaginal smears, it is necessary to study at the same time the«acidophilic index»the«acidophilic index.»the«pycnotic index»and also the value A/P i.e. acidophilic index/pycnotic index Oestrogenic activity is characterized by the increase of those two values but it seems that they need a different treshold ofœstrogenic activity to be modified. This method makes possible to gain some information on the quality of theœstrogenic reaction and also on the duration of the activity ofœstrogenic drugs. Besides, when the value A/P is higher than 1, acidophilia is abnormal and it becomes impossible to appreciate exactly the degree of theœstrogenic reaction.Monochromatic technics do not permit a comparativo study of these values. They must be discarded. It must be emphasized that polychromatic methods, like that described by Shorr, are not more difficult than monochromatic technics.