BACKGROUND: Because there is difficulty in the addition of known preservatives to oil in water emulsion such as propofol, ethylenediaminetetraacetic acid (EDTA) added to this may formulate for the antimicrobial activity; however, this formulation has side effects such as hyperlipidemia and pain on injection. We have developed a newly formulated poloxamer-solutol propofol which is considered to be free from hyperlipidemia. The aim of this study was to evaluate the possibility of bacterial growth in poloxamer-solutol formulated propofol compared to original propofol and EDTA added propofol. METHODS: Broth cultures (100nl) of four standard preservative efficacy test organisms (Staphylococcus Aureus, Pseudomonas Aeruginosa, Escherichia Coli, Candida Albicans) were added to 9.9 ml of four test formulations. Subjected formulations were original propofol (AstraZeneca Co, 1% solution, UK), EDTA added propofol (0.0055% EDTA added propofol), Poloxamer-Solutol formulated propofol (poloxamer 188/407 and solutol mixture), and normal saline at approximately 200 colony forming units/ml. The test formulations were incubated at 25degreesC and 32.5degreesC (Tryptic soy agar medium for bacteria and Sabrouraud dextrose agar medium for fungus) and tested for viable counts after 24 and 48 hours. RESULTS: Original propofol supported the growth of all microorganisms at both temperature and time. EDTA added propofol inhibited the growth of microorganisms more than the original propofol, but not so much as the poloxamer-solutol formulated propofol. Saline showed a similar pattern as EDTA added propofol. CONCLUSIONS: Poloxamer-solutol formulated propofol possesses more bacteriostatic activity against all four microorganisms than the original and EDTA added propofol.