This paper reports on the preliminary results of an on-going prospective evaluation of an `intelligent' mammography workstation. This workstation can provide to radiologists a `second opinion' as to the location of suspicious lesions on mammograms. The workstation consists of a high speed computer, film digitizer, image archive, and both hard and soft copy output. Running on the workstation are automated computerized schemes for the detection of breast masses and clustered microcalcifications. In the current study, all screening mammograms are digitized on the workstation and then analyzed by the computerized schemes. The preliminary results for the first 37 days (573 patients) have been analyzed. Although follow-up to establish truth has not been done for all patients, the two schemes detected the lesion in 10 of the 14 patients who had a `suspicious' lesion present mammographically. Three of the lesions missed by the computer were found to be benign either at biopsy or after further work-up, and the fourth one is scheduled for further work-up. For two patients, a cluster of microcalcifications was detected by the computerized scheme that was initially missed by the radiologist. The false positive rate was 1.2 false masses and 0.87 false clusters per image. Over 70% of the false positive masses were caused by nodular densities and approximately 50% of the false cluster included obviously benign calcifications. The results from this ongoing study will be used to plan a full-scale clinical study.