Euphorbia tirucalli L. (Family, Euphorbiacae) a succulent cactus-like plant growing to a height of about 10 m, was introduced from Africa as a garden plant. E. tirucalli Grows in arid zones as well as zones that are more mesophytic, the species makes a good living fence post. The plant grows well in dry regions or land that is not suitable for growing food. E. tirucalli is called petroleum plant because it produces a hydrocarbon substance very much like gasoline. Whole plant harvesting is worthwhile from energy point-of-view with rubber, petroleum, and alcohol as energy products and resins, which may find use in the linoleum, oilskin, and leather industries. The charcoal derived there from can be used in gunpowder. Many pharmacological activities of Euphorbia tirucalli has been documented by many workers as molluscicidal activity (Jurberg et al., 1985; Tiwari et al., 2003), antibacterial activity (Lirio et al., 1998), antiherpetic activity (Betancur-Galvis et al., 2002) and anti-mutagenic (Rezende et al., 2004). Latex also shows co-carcinogenic (Gscwhenot and Hecker, 1969) and anticarcinogenic activities (Hecker, 1968). The inhibition of the ascitic tumor in mice has also been reported by Valadares et al. (2006). In the northeast region of Brazil, the latex of Euphorbia tirucalli is used; as an antimicrobial; a laxative agent; to control intestinal parasites; to treat asthma, cough, earache, rheumatism, verrucae, cancer, chancre, epithelioma, sarcoma, skin tumors and as a folk remedy against syphilis (Correia, 1994; Betancur-Galvis et al., 2002). Exposure to Euphorbia tirucalli has been suggested as an important environmental risk factor for African Burkitt’s lymphoma (Van den Bosch et al., 1993; Imai et al., 1994; MacNeil et al., 2003). In E.tirucalli 4-deoxyphorbol ester, has been clinically documented to enhance Epstein-Barr virus (EBV) infection, causing damage to immune cell’s DNA and induce rearrangement in the chromosomes, particularly in chromosome 8, which causes a suppression of the immune system (Aya et al., 1991; Jurberg et al., 1985; Almeida, 1993; Costa, 2002; Tiwari et al., 2003). The stem contains alcohol eufol, -euforbol and taraxasterol, tirucallol (Costa, 2002; Almeida, 1993), hentriacontene, hentriacontanol, the antitumor steroid -sitosterol, taraxerin, 3,3’-Di-O-methylellagic acid, ellagic acid, and a glycoside fraction which hydrolyses to give kampferol and glucose. The whole plant contains 7.4% citric acids with some malonic and some bernstein (succinic) acids (List and Horhammer, 1969), The latex of Euphorbia tirucalli contains as irritant constituents ingenane- and tigliane-type diterpene esters derived from the parent alcohols ingenol and phorbol (Furstenberger and Hecker 1986). The main irritant constituents are isomeric 12,13-acetates, acylates of phorbol as well as 3-acylates of ingenol (Imai et al., 1994). In the acyl moiety of phorbol esters investigated in detail, an increasing number of C-atoms or an increasing number of double bonds at a fixed number of C-atoms leads to an increase of irritant activity. As compared to their saturated analogs, corresponding unsaturated phorbol esters exhibit similar irritant activities (Duke, 1983). On the other hand, by an increasing number of conjugated double bonds in the acyl moieties of phorbol esters, the promoting activity is decreased, thus indicating that irritant activity is a necessary, but insufficient, requirement for promoting activity of phorbol esters (Furstenberger and Hecker 1977). The latex contains 53.8-79.9% water and water solubles nad 2.8-3.8% caoutchouc. Fresh latex contains a terpenic alcohol, isoeuphoral (C30H50O), Dried latex contains no isoeuphorol but a ketone euphorone (C30H48O) (Uzabakiliho et al., 1987). Resin, however, is the principal constituent (75.8-82.1%) of the dried latex. The stem contains hentriacontene, hentriacontanol, the antitumor steroid 4-deoxy-phorbol ester, beta-sitosterol, caoutchouc, casuariin, corilagin, cycloeuphordenol, cyclotirucanenol, ellagic acids, euphorbins, euphol, euphorone, euphorcinol, gallic acids and glucosides (Khan and Malik, 1990). Therefore the present study has been undertaken to investigate the antimicrobial activity of leaf extract of Euphorbia tirucalli by disc diffusion method.