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Chemical profile of the essential oils of three Eucalyptus species viz. Eucalyptus citriodora, Eucalyptus lanceolatus and Eucalyptus globulus was determined by GC-MS. Seventeen components were identified in E. globulus oil, among them p-cymene (31.88%), eucalyptol (17.47%), a-pinene (17.18%), were the major components. Major components of E. lanceolatus oil were p-cymene (54.75%), eucalyptol (18.88%) and β-phellandrene (18.86%) and four major monoterpenes compounds viz., Isopulegol (51.12%), β-citronellal (29.15%), L-isopulegol (11.49%) and citronellyl acetate (5.77%) were identified in E. citriodora oil. Antimicrobial activities of the essential oils were evaluated against seven bacterial and three plant pathogenic fungal strains. E. citriodora oil inhibited the growth of all the test bacterial strains with the significant inhibition against Pseudomonas alcaligenes (23±0.73 mm) and also showed potential antifungal activity especially against Alternaria alternata (IC value 0.16±0.012%). E. lanceolatus essential oil showed strong antibacterial activity against Micrococcus luteus (33±0.97 mm) and Bacillus subtilis (27±0.69 mm) and also possesses moderate antioxidant activity (IC value 534±9.31 µg/ml) in DPPH system. E. citriodora and E. globulus showed negligible radical scavenging activity. Cytotoxic potential of the E. citriodora oil was found maximum against breast (T 47D) and prostrate (PC-3) cancer cell lines with 86% and 76% growth inhibitions, respectively. The present study emphasizes that E. citriodora essential oil is a potential inhibitor of different bacterial and fungal strains and also possesses significant cytotoxic activity against human cancer cell lines, whereas of E. lanceolatus essential oil is a noteworthy free radical scavenger. [ABSTRACT FROM AUTHOR]