Abstract: The invention concerns a transdermal therapeutic system comprising the active substance 17-.beta.-estradiol and optionally further active substances, with a laminated structure comprising a backing layer which is substantially impermeable to moisture and impermeable to active substance, one or more matrix layers and, where non-adhesive matrix layers are present, an adhesive layer, characterized in that the concentration of the dissolved estradiol in all matrix layers and, where an adhesive layer is present, in the adhesive layer lies between its saturation concentration in dry condition und its saturation concentration in moist condition, whereby the term "dry condition" is understood to mean that the base material is in equilibrium with a gas phase with less than 10% relative humidity and the term "moist condition" is understood to mean that the base material is in equilibrium with a gas phase with more than 90% relative humidity.