The file size of images generated using digital mammography systems varies between 8 MB and 50 MB. The amount of data to be stored in digital screening programs is huge. Image compression may be helpful. In this study 8491 digital and digitised mammography images are compressed using 14 lossless compression schemes. The results show that using lossless image compression, the total amount of data to be stored can be reduced by a factor of 1.3 to 6.9 without loss of image quality. The actual data reduction depends strongly on the selected compression algorithm and the systems used to acquire and process the mammograms. The JPEG-LS and JPEG 2000 algorithms, both included in the DICOM standard, prove to be promising algorithms for screening programs because of the high compression ratios.