The macrophages in human Fallopian tubes of women in the reproductive and postmenopausal periods were examined with a focus on their morphological properties by immunohistochemical staining and transmission electron microscopy. The fine structure of the smooth muscle cells in the Fallopian tubes was also investigated during the reproductive period. For immunohistochemical staining, we used two monoclonal antibodies that were specific for human macrophages, namely PM-1K and PM-2K. PM-1K recognizes human monocytes/ macrophages corresponding to CD68, and PM-2K recognizes tissue macrophages. PM-1K-positive cells were always present and their numbers increased significantly during the menstrual and early to mid-secretory phases. In contrast, relative numbers of PM-2K-positive cells were small throughout the menstrual cycle. In the postmenopausal period, few PM-1K-positive cells were detected, but PM-2K-positive cells remained. The macrophages during the secretory phase in the endosalpingeal stroma had well-developed intracytoplasmic organelles, but relatively few cytoplasmic vacuoles and granules. In the same phase, many cells of the monocyte/macrophage lineage appeared in the vascular lumen of the endosalpingeal stroma. The macrophages during the menstrual phase had well-developed intracellular organelles, with cytoplasmic vacuoles and granules of various sizes and configurations. During the late secretory phase, just prior to menstruation, the smooth muscle cells contained few cytoplasmic filaments but electron-lucent or electron-dense lysosome-like bodies were seen. These findings suggested the presence of macrophages in human Fallopian tubes. It is possible that such macrophages might be involved in the physiological functions of the tubes during the reproductive period and moreover that they might participate in the reconstruction of the muscle layer of the tubes.