In the course of their practice 2 gynecologists have conducted a program of screening for breast cancer in 1538 patients ages 35-49 years and on 1102 patients ages 50 or older. The screening protocol of breast examinations, thermography, and selective mammography is described. Twenty-four (9/1000) breast cancers were found, 12 in each age group. Eight of these (3/1000) were clinically occult (6 in the younger age group, 4/1000) and were detected by abnormal thermograms followed by mammography. Of the 12 cancers in the 35-49-year-old age group, 6 were discovered at the first screening, and the other 6 by thermographic changes at intervals of 6-24 months. Thermographic screening is more accurate than breast examination alone, but less accurate than if mammography is included. However, since routine annual use of the latter in younger women still raises concerns about x-ray dosage, thermography is a valuable adjunct to physical examination alone. When it is abnormal, mammography is indicated. The 3 complementary methods can reveal about 9 of 10 preclinical cancers in young women.