This study was carried out to investigate the constituents and antimicrobial activity of Gardenia ternifolia.. Gardenia ternifolia Schum. & Thonn. is a small tree or shrub in the family Rubiaceae..GC- MS analysis of Gardenia ternifolia oil revealed the presence of 14 constituents dominated by i) 9,12-octadecadienoic acid (Z,Z), methyl ester (17.87 % ) ii) stigmast-7-en-3-ol, (3.beta.,5.alpha.,24S)- (12.66%) iii)oleic acid(8.50%) iv) hexadecanoic acid methyl ester (7.37%) and v)n-hexadecanoic acid(7.33%). The oil was screened for antimicrobial activity against five standard human pathogens: Bacillus subtilis(G+ve), Staphylococcus aureus(G+ve), Escherichia coli(G-ve), Pseudomonas aeroginosa(G-ve) and the fungal species Candida albicans. Gardenia ternifolia oil showed significant activity against Pseudomonas aeroginosa, Staphylococcus aureus and Escherichia coli.