In the present study, growth inhibitory effect of garlic, shallot and onion extract against wide range of bacteria and fungi was observed. The antimicrobial activity of garlic, shallot and onion extracts has been reported earlier. Ascalin is a new anti-fungal peptide, which has been isolated by Wang and Ng from shallot bulbs. Yin and Tsao have reported that antifungal activity of seven Allium plants including shallot, decrease when the extracts are subjected to increasing temperature. The significant observation of the present study was heat stability of shallot extract at 121 °C and retention of antimicrobial activity after drying. However, garlic and onion were sensitive to these treatments. It is expected that antimicrobial compound of shallot was different from active compounds of onion and garlic. However, fresh extract of garlic was more active than fresh ex tract of shallot and onion. MIC values of shallot extract for bacteria and fungi indicated that fungi were more sensitive than bacteria. No obvious differences between the sensitivity of Gram-negative and Gram-positive bacteria, yeasts and filamentous fungi, were observed. The only exception was Pseudomonas aeruginosa that tolerated 20 mg ml concentration of shallot extract. This finding was contradictory to that of Ashrafief el al. in which Pseudomonas aeruginosa was sensitive to aqueous shallot extract. According to physico-chemical analysis (data not shown) the antimicrobial compound is likely to be a flavonoid with CI4H1806 formula. However, this needs confirmation. Based on these results, we speculate, better potential for shallot extract in food preservation at high temperature as well as in the therapy of dermatomycoses.