In 147 cases of mammary carcinoma, 388 serial mammographies were performed before final treatment. The average retrospective observation time was 27 months with a range of two months to 11 years. The number of serial mammographies per case ranged between two and 11. The tumor volume doubling times (TV); obtained by measuring the growth of the tumor nucleus shadow in the mammographies, ranged from 44 to 1869 days with an average of 212 days. No correlation between volume doubling time and histologic differentiation could be found. One hundred of these cancer patients were found in a screening population of 22,000 women receiving serial mammographies in a time period ranging from two to 16 years. An additional 40 cancer patients surfaced in this group without roentgenologic but with foregoing clinical or thermographic abnormalities before final diagnosis. An additional 21 cancer patients surfaced without any foregoing abnormalities. The follow-up tumor ranged between three months and two years with a mean time of one year and nine months. Not considering tumor size, pathologic-thermographic signs appeared with greater frequency the faster the tumor grew. Theoretically, an average of more than 16 years should elapse before an initial tumor cell develops into a 10-mm primary mammary carcinoma (30 doubling times). Therefore the length of time necessary for a 2-mm tumor to grow to a size of 10-mm is, on the average, four years.