Abstract: The invention concerns a method and arrangement for measuring the bone mineral content in the skeleton in a body part, which is irradiated from one side with X-radiation which is detected on the opposite side of the body part. The X-radiation has two energy levels, the detected radiation is analyzed and the thickness of the body part is determined. The analysis takes account of the thickness of the body part and in order to calibrate the measuring process, a reference object of known composition is measured. The arrangement comprises: means (3) for generating X-radiation at two energy levels which means is disposed on one side (2a) of a casing (2) whose shape is adapted to that of the body part and which means is directed towards the latter. A radiation-detector matrix (4) disposed on the opposite side (2b) of the casing detects the X-radiation received.