Contact pressure from a transducer is controlled in medical diagnostic ultrasound imaging. Rather than measuring pressure directly using a pressure sensor on the transducer, the compression of tissue within the patient may be measured using ultrasound scanning. The desired amount of compression in the region of interest for diagnosis may be obtained. For example in breast imaging, the desired compression for imaging a portion of the breast is compared to compression measured from ultrasound data. Once the desired tissue compression is achieved, the pressure applied by the transducer is maintained while the diagnosis scan occurs. For example, a robotic arm locks or otherwise maintains the pressure during scanning.