A correlated ultrastructural and immunofluorescent study of anchoring fibrils and their principal constituent, type VII collagen, has been carried out on lobular epithelium from the normal adult human breast at different times in the menstrual cycle. Throughout the cycle, characteristic, cross-banded anchoring fibrils were seen inserting into the area of lamina densa opposite the myoepithelial hemi-desmosomes and in contact with anchoring-plaques. Strong immunofluorescent staining was seen in the full thickness of the zone between the basement membrane and the delimiting fibroblasts. The data establish anchoring fibrils and their type VII collagen nature as readily identifiable components of the epithelial-stromal interface in breast tissues and their significance, especially in the diagnostic context, is discussed.