http://pjpr.net INTRODUCTION: The knowledge of medicinal plants has been accumulated in the course of many centuries based on different medicinal systems such as Ayurveda, Unani and Siddha. In India, it is reported that traditional healers use 2500 plant species and more than hundred plant species serve as regular sources of medicine (Sheng-Ji, 2001). Even in the developed countries, like USA 25% of prescription for pharmaceutical drugs contains one or more substances of plant origin (Dev et al., 1997). A large number of plants with therapeutic properties are quite astonishing. It is estimated that around 70,000 plant species, from lichens to trees, have been used at one time or another for medicinal purposes. (Das et al., 2003). The value of ethno-medicine and traditional pharmacology is gaining recognition because the search for potential medicinal plants is successful if the plants are chosen on ethno-pharmacological basis. Phytochemical components are important sources of potential pharmacological, chemotherapeutic and toxic activities (Lawal et al., 2005). The continuous development of antibiotically resistant strains of microbial pathogens, such as methicillin resistant Staphylococcus aureus (MRSA), penicillin-resistant Streptococcus pneumoniae (PRSP) and vancomycin- resistant enterococci (VRE), is a growing problem and it is therefore, extremely important to discover and develop new antimicrobial compounds (Tally et al., 1999). The antimicrobial compounds from plants may inhibit bacteria through different mechanisms than conventional antibiotics and could therefore be of clinical value in the treatment of resistant microbes (Eloff et al., 1998a). The selection of the plant group for this investigation was based on uses in traditional medicine, since many Combretum and Terminalia species are well known medicinal plants both in Africa and Asia (Watt and Breyer-Brandwijk, 1962; Hedberg et al., 1982). Alcoholic extract of Terminalia arjuna increased the force of contraction of frog heart (Gupta et al., Tariq Javed* 1 , Sana Riaz 2 , Muhammad Uzair 1 , Ghulam Mustafa 3 , Ayesha Mohyuddin 4 , Bashir Ahmad Ch 1 . Biological activity of Terminalia arjuna on Human Pathogenic Microorganisms. Research Article ABSTRACT World’s population relies chiefly on traditional medicinal plants, using their extracts or active constituents. Terminalia arjuna of family Combretaceae reported to be effective as aphrodisiac, expectorant, tonic, styptic, anti-dysenteric, sweet, acrid, purgative, laxative, diuretic, astringent, cirrhosis, cardio protective and cancer treatment. In present study, antibacterial, antifungal, brine shrimp lethality and phytotoxic effect of Terminalia arjuna was performed. Our results showed that methanolic extract of Terminalia arjuna leaves has moderate antifungal effect against Microsporm canis and fruit extract possess good antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa. Moreover, Dichloromethane extract of Terminalia arjuna bark and fruit possess moderate phytotoxic activity. Received: Aug 11, 2015 Revised: Oct 10, 2015 Accepted: Jan 11, 2016 Online: Jan 27, 2016 1 Department of Pharmacy, Bahauddin Zakariya University (BZU), Multan, 60000 Pakistan 2 The Women University, Multan, 60000 Pakistan. 3 Lahore Pharmacy College, (LMDC) Lahore, 54000 Pakistan 4 The University of Management and technology Lahore, Pakistan Keywords: Antibacterial, Antifungal, Phytotoxicity, Terminalia arjuna *Corresponding Author: Dr. Tariq Javed Address: Faculty of Pharmacy, Bahauddin Zakariya University, Multan, Pakistan Phone# +92 3214960825 e-mail: tjavedpk@gmail.com