Based on two pretreatment evaluations, doubling time (DT) was calculated in 75 cases of invasive breast cancer (BC). The cases studied were more or less equally distributed between three DT groups: fast-growing tumors (DT less than 90 days), intermediate cases (DT between 90 and 180 days), and slow-growing tumors (DT greater than 180 days. A correlation was found to exist between DT and patient age and, to an even greater extent, between DT and pathologic prognostic indicators such as histologic grading and nuclear grade. Inflammatory symptoms were not associated with DT, but were closely related to the size of the tumor and regional lymph node involvement. The date of detection of distant metastases depended heavily on the DT of the BC:BC with shorter DT = earlier metastatic spread. The presence of inflammatory signs was also decisive: within each DT category, inflammatory BC metastases were both more frequent and precocious.