Microbiopsies of human Fallopian tube fimbrial epithelium were obtained during routine gynecological operations, and during pregnancy while undergoing hysterectomy in the first trimester or cesarean section in the third trimester. Specimens were studied under light and electron microscopes utilizing histo- and cytochemical techniques. Large juxtanuclear globules were demonstrated in the ciliary cell at all stages of the cycle. During the proliferative phase, these globules contained large lipid droplets and glycogen rosettes. The content of the globules in the early luteal phase was mostly amorphous electron-lucid material which failed to stain with PAS, alcian blue and the Millon reaction. However, reaction products of acid phosphatase as well as calcium precipitate were scattered in them as discrete granules. The same type of globule was found in early pregnancy. During late luteal phase and late pregnancy, the content of the globule was once again composed of lipids and glycogen. It seems that lipid and glycogen accumulate during the preovulatory phase, while depletion and dispersion of these substances occur in the periovulatory phase, probably due to increased energy utilization. Late luteal phase revealed subsequent replenishment of these reserves, as was also revealed in late pregnancy.