To investigate the effect of several bactericides and fungicides against fruit & vegetable decay grapefruit seed extract(GFSE) was tested in a dilution solution. GFSE was shown to be effective against decay and rind breakdown and to extend the shelf-life of fruits and vegetables during storage and tiansport. Antimicrobial efficiency of GFSE on a wide spectra of gram + & - bacteria, moulds and yeasts was demonstrated by the measurement of minimal inhibitory concentrations performed (Bacteria 10-500ppm, Fungi:250-1,000ppm, Yeasts:100-250ppm). GFSE was separated and extracted into water-soluble fraction, water-insoluble and non-dialyzed fraction to isolate the antimicrobial substances. The water-soluble fraction showed the most active antimicrobial effect. The antimicrobial substances were isolated by gas chromatography. As the result of the isolation using GC, Peak-D was found to be the antimicrobial compound in GFSE. The identification of the most antimicrobial substance was carried out by using GC-MS.