Since ancient times medicinal plants have had an important place in preventing and treating disease. Many conventional drugs originate from plant sources, including aspirin (from willow bark), the heart drug digoxin (foxglove), and morphine (opium poppy). Scientific and modern pharmaceutical interest in medicinal plants is largely due to the need for new, safe drugs, but they remain important to many people in the developing world who do not have access to modern medicines. Several medicinal plants have been used for uterine proposes in the developing world (Gruber & O’Brien, 2011). However, the mechanisms of action of such the plants have never been elucidated. The aims of the studies in my laboratory are therefore to investigate the effects of some medicinal plants on myometrial physiology. Plant extracts were prepared from botanical sources, standardized and validated. Phytochemical screening of the crude extracts was analysed using gas chromatography-mass spectrometry. All separated compounds were identified from the recorded mass spectra by comparison with the mass spectra from the NIST and Wiley libraries. Animal cares, environmental conditions, and uses followed the guidelines of Laboratory Animal Resources and the procedures of the experiment were approved by the Institutional Animal Care and Use Committee. Rats were humanly killed. The uteri were removed and the strips of longitudinal myometrium isolated. Isometric force was measured in organ baths and vehicle and time controls were always performed. The effects of plant extracts on spontaneous and agonist-induced contraction in the uterus were investigated, and the dose response range determined. Using a pharmacological approach, the parts of the myometrial excitation contraction pathway which were affected by the extracts, were dissected. This approach provided a good amount of mechanistic information. The results showed that some of the plant extracts are potent inhibitors (Buddhakala et al, 2008; Munglue et al, 2012) whereas others are potent stimulators (Promprom et al, 2010; Lijuan et al, 2011) for the uterus. The parts in the pathways affected were extract specific and reveal many therapeutic targets, including calcium entry and sarcoplasmic reticulum release, and stimulating the NO-cyclic guanosine monophosphate relaxant pathway. Taken together, these data will give us a better understanding of how medicinal plants work on the uterus and the results of these findings can be applied in other areas of smooth muscle physiology, as well as pharmacy and medicine.