A total of approximately 10,000 breast thermograms was analyzed and further subdivided into symptomatic and asymptomatic groups of patients of 55 and 45 per cent, respectively. Positive, or abnormal, mammatherms were recorded in 36 per cent of thesymptomatic and 23 per cent of the asymptomatic groups. Of the 306 histologically confirmed cancers, 270 were in the symptomatic group of patients and 36 were clinically occult. Clinical accuracy was enhanced by the supplemental use of mammography and thermography. Sixty-one per cent of the occult cancers were suspect by thermography and if, in the asymptomatic group, thermography had been used as the initial screening procedure and mammography performed only on those with abnormal thermograms a yield of 21.4 cancers per 1,000 mammographic examinations would have been realized. Thermography is an innocuous examination that can be utilized for preliminary screening of asymptomatic women to focus attention upon those who should be examined more intensively because of greater risk of breast cancer.