I. INTRODUCTION: STRATIFICATION OF TUBAL ENDOCRINE RESPONSE THE FALLOPIAN TUBE has, until very recently, been essential for human reproduction. Sperm transport and capacitation, ovum transport, fertilization, and early embryogenesis are fundamental reproductive events that normally take place in its lumen. Although in recent times in vitro fertilization (IVF) procedures have sought to mimic the tube's luminal environment, the still limited success of IVF carries the certain implication that more detailed knowledge of fallopian tube function may not only improve treatment of its anatomical and physiological disturbances but also should provide a better empirical basis for its in vitro counterpart. Fallopian tube physiology is exquisitely dependent on hormones. The responsive tissues include the muscle layer (or myosalpinx), the vasculature, the epithelium (or endosalpinx) and, most important, the fluids contained in the lumen. Intricate tiers of endocrine influences and responses in the human fallopian tube need to be disentangled, ranging from water-soluble, membranereceptor-mediated (and rapid) neuroendocrine, endocrine and paracrine actions on the one hand through to nuclear/cytosol-receptor-mediated (and relatively slow) steroid hormone actions on the other.