The purpose of the present study is to investigate the ultrastructure and immunohistochemistry of the stromal cells and terminal nerve fibers in human fallopian tube ampullar mucosa to achieve a detailed characterization of this tissue to permit a better assessment of possible functions. Tissues were obtained during surgery or at autopsy from 26 patients. Specimens were studied by the conventional histologic technique, immunohistochemistry (Cx43, synaptophysin, neurofilament proteins, and S-100 protein), and electron microscopy. Gap junction and nerve terminal frequency between stromal cells were studied by direct assessment on ultrathin sections in the transmission electron microscope. Gap junctions were observed between the cytoplasmic processes of subepithelial stromal cells. There were approximately 23 gap junctions per 73 nucleated stromal spindle cells. Immunohistochemistry using Cx43 antibody confirmed the dot-like distribution of gap junctions. The frequent and intimate association of stromal cell processes with nerve terminals was also demonstrated. Nerve terminals were immunostained by antibodies to nerve-specific molecules and ultrastructurally as axonal profiles containing dense-cored granules or empty vesicles. Analysis of nerve terminal frequency revealed 18 nerve profiles containing 51 axonal profiles per 73 nucleated stromal spindle cells. The present paper documents the participation of autonomic nerve endings and gap junctions in the stromal cell network in human fallopian tube stroma. Similarities to the unique anatomical unit referred to as the'neuro-reticular complex'in bone marrow tissue (Yamazaki and Allen, 1990) are discussed.