As medical image databases are connected together through PACS, those medical images may suffer from security breaches if not protected. If a medical image is illegally obtained or if its content is malevolently changed, the patient?s privacy or health care to be provided will certainly be undermined. To solve this problem, this study proposes a steganographic method for mammograms, which hides patients? information in mammograms without changing their important details. In particular, the proposed method can extract the hidden information from stego-mammograms without the aid of the original images. This study also utilizes a watermarking technique, which masks the contents of the mammogram, for providing mammograms protection against illegal access and malevolent modifications. This watermark can be removed to reveal the masked mammogram when authorization for viewing is given.