In the late 1950's Lawson (1) used thermographic scanners to produce thermal images of the breasts. His findings, subsequently confirmed by Williams et al. (2) and Gershon-Cohen et al. (3), indicated a usefulness of the technic in the assessment of suspect breasts. In the United States, thermography has previously been performed with units that require from four to twelve minutes to make a clinical scan. Such a long scanning period imposes the rather severe requirements that: 1. The basal conditions remain constant over the scanning period 2. Any interference contributed by external sources uniformly contributes to the whole scan 3. The patient remains still throughout the scanning time. In order to overcome or mitigate these requirements we have used a solid state, liquid nitrogen cooled scanning unit which produces a scan of the area from the navel to the neck in about thirty seconds. The differential temperature sensitivity is of the order of 0.2° C. The image or thermogram, composed of a montage of about 40,000 information bits, is produced on a facsimile recorder which has three desirable features: (a) a long gray scale, (b) the possibility of viewing the thermogram as the patient is scanned, and (c) a paper similar to that used by the news services for the transmittal of pictures which is quite inexpensive. We are presently investigating the clinical application of rapid scanning thermography in the assessment of suspect breasts, peripheral circulatory disorders, placental localization, and rheumatoid arthritis. Other applications of thermography which might produce useful clinical information are being explored. All patients referred for mammography have also been thermographed. The initial interpretation of the thermograms has been made with no knowledge of the nature of the suspect breast other than physical examination at the time of thermography. Thus, the adequacy of the thermogram diagnosis can be compared with that of mammography and, in some cases, with both mammograms and pathologic findings. Our limited experience indicates that the technic is capable of detecting carcinoma of the breast with a high degree of accuracy. The major interpretative error has been misidentification of inflammatory lesions or islands of functioning breast tissue surrounded by multiple cysts as malignant lesions. In this respect investigation of comparative temperature levels is current^ under way. The information derived in those cases with false or negative mammograms, however, suggests that breast thermoscans may prove to be of great assistance in the accurate clinical evaluation of lesions of the breast.