The invention relates to a method and a device for ascertaining a time-dependent blood pressure curve. Time- and volume-dependent blood flow values are detected in a noninvasive manner in a tissue section with a good blood flow as photoplethysmography values P(t) using a photoplethysmography sensor. A data processing unit transforms the photoplethysmography values P(t) into blood pressure values B(t) by carrying out a transformation rule. An output and storage unit at least temporarily stores the transformed blood pressure values B(t) as time-dependent blood pressure values and transfers said values to an external or internal display and/or storage unit arranged downstream.