Talinum paniculatum (T. paniculatum) has long been used in Thai herbal recipes because of its various therapeutic properties such as improving vitality or treatment of type-2 diabetes, inflammatory skin problems, gastrointestinal disturbance and general weakness (Shimoda et al, 2001; Pak et al, 2005). T. paniculatum is also believed to be beneficial for female reproductive system by inducing lactation and restoring uterine functions after post-partum period (Manuhara et al, 2012). Although, the plant has been reported to influence the female reproductive system, but there is no scientific data regarding to clarify the effects on the uterus to support its therapeutic relevance. Therefore, the purpose of this study was to investigate the effects of T. paniculatum leaf extract on uterine contractility and its possible mechanism(s) on adult female virgin rats. In this study, animal cares, environmental conditions, and uses followed the guidelines of Laboratory Animal Resources, National Research Council of Thailand. The procedures of the experiment were approved by the Institutional Animal Care and Use Committee, Suranaree University of Technology, Nakhon Ratchasima, Thailand. The rats (200-250 g) were humanly euthanized by CO2 asphyxia and uteri were removed. Isometric force was measured in strips of longitudinal myometrium (1-2 mm x 0.5 mm x 10 mm) in organ baths containing physiological Krebs’ solution maintained at 37 °C, pH 7.4. The effects of T. paniculatum leaf extract at certain concentration level (IC50; 1.67 mg/mL) on spontaneous contraction and agonist-induced contraction such as high KCl (40 mM) solution, Bay K8644 (1 μM), and oxytocin (10 nM) were observed. All values were analyzed by Paired student t-test. A probability level less than 5% (P<0.05) was considered statistically significant. The results showed that spontaneous uterine contractile activity was found to be dose-dependently inhibited by the extract (n = 5). In addition, the extract significantly inhibited the contraction induced by high KCl solution (P<0.01) (n = 5). In Bay K8644 and oxytocin studies, the extract significantly relaxed the uterus in a time-dependent manner (P<0.05) (n = 5). Interestingly, the extract could potentially inhibit oxytocin-induced contraction in the absence of external Ca2+ (n = 7). Taken together, the data implied that T. paniculatum produces tocolytic effects on both spontaneous and agonist-induced contractions. The possible mechanisms may be due to the blockade of Ca2+ influx via L-type Ca2+ channel and Ca2+ efflux from internal store.