Abstract: The effects of Morinda citrifolia (Rubiceace) extract on coronary perfusion pressure, contractility and heart rate of isolated rats hearts were studied by using the technique of Langendorff system. Sodium nitroprusside (SNP) was used as a positive control and standard while saline was used as negative control. The extract at doses of 1.0 and 10 mg, respectively showed a significant decrease in coronary perfusion pressure compared with saline. The extract dose of 10 mg showed a maximum decrease in coronary perfusion pressure, developed tension and heart rate. The next part of the study was to investigate the involvement of nitric oxide in the coronary vasodilatory effects of the extract. The inhibitor of nitric oxide synthesis, NG-nitro-L-arginine metil ester (L-NAME) 300 μM was perfused together with Krebs-Henseleit solution in the heart for test group, while the time-matched control group without L-NAME. L-NAME did not abolish the decrease of coronary perfusion pressure and developed tension by the second injection. So, nitric oxide is not involved in the mechanism of coronary vasodilation. In conclusion, the M. citrifolia extract decreased coronary perfusion pressure and developed tension.