Abstract: Traditional Chinese Medicine is largely based on experience and is guided by a holistic concept. Theories such as the "yin-yang" theory and "five-elements" theory embrace the view that treatment is targeted at correcting an underlying imbalance. Ying-yang literally means "opposites" and refers to opposing influences such as positive and negative forces. The five-element theory is named "Wu Shing" in Chinese and expounds that everything is maintained in kinetic balance under the movement of five elements. Prescription of herbs based on these theories may comprise a single herb or more commonly a mixture of herbs in differing amounts. The constituents of herbal products can cause adverse effects. Although natural products are widely used as food or as medicines for humans they can alter the labeling of blood constituents with technetium-99m (99mTc) as wells as the shape of red blood cells. 99mTc is one of most used radionuclide in nuclear medicine and in basic research. It was related by some authors that natural and synthetic drugs may alter the process of radiolabeling. Sechium edule (chayotte) is a vegetable very spent in the human nutrition as the popular medicine due its properties such as the diuretic and the hypotensor effects. We evaluated the influence of a chayotte (Sechium edule) extracts (decoct and macerated) on the morphology of red blood cells and on the radiolabeling of blood elements. In our study, blood was withdraw from Wistar rats which were treated with chayotte extracts (0.1g/mL) during 15 days. After that, blood was incubated with stannous chloride (SnCl2) for 1 hour. Elapsed this time 99mTc as Sodium pertechnetate (NaTcO4) was added and the incubation continued for more 10 minutes. Plasma (P) and blood cells (BC) were isolated, also precipitated with trichloroacetic acid (TCA 5%) and soluble (SF) and insoluble fractions (IF) were separated. For the morphology analysis, samples of the blood were collected and smears were prepared. The blood smears were dried, fixed and stained. The analysis was done by video optical microscope using image pro-plus program. In our results it was observed that the referred extracts were capable to alter the radiolabeing of blood elements together with the morphology of red blood cells. Similar results were noticed in a in vivo study with a Mentha crispa L. estract (mint). The effect of the chayotte extracts probably, could be explained by the generation of activity metabolites with oxidant properties which might be altering the stabilizing of the red blood cell membrane as the radiolabeling of blood elements.