Proboscidea louisianica (Mill.) Thell is a spreading annual plant. Young fruits are edible. Seed oil contains: among others-linoleic. oleic and palmitic acids beside some sterols. The claws of the mature seed pods are traditionally used against rheumatic pain. In this study the constituents of Proboscidea louisianica seed oil have been characterized by GC-MS and the antimicrobial activity of the oil has been assessed. Fifteen components have been detected by GC-MS analysis. Major constituents are: 9,12-octadecadienoic acid methyl ester(43.99%), 9-ctadecenoic acid (Z) methyl ester(25.40%), hexadecanoic acid methyl ester(12.01%) and methyl stearate(8.89%),The antimicrobial activity of the oil was evaluated using the diffusion assay against: Gram positive: Staphylococcus aureus and Bacillus subtilis; Gram negative: Escherichia coli and Pseudomonasa aeruginosa and the yeast Candida albicans. The oil showed moderate anticandidal activity. It also exhibited weak activity against Staphylococcus aureus. However, it failed to exhibit activity against other test organisms