Cholesterol reducing abilities of six strains of Lactobacillus acidophilusincluding ATCC 4356, B, E, Farr, LA-1 and N-1 were investigated in vitro. All thesestrains were able to reduce cholesterol at various levels in the broth system used inthis study. Among the strains tested, L. acidophilus ATCC 4356 demonstrated the bestcholesterol reducing ability at 57 and 71% in the presence of oxgall and cholic acid,respectively, in the broth. Results from the acid tolerance and growth in oxgall studiesdemonstrated that these L. acidophilus strains would likely survive in the humangastrointestinal tract, where acid and oxgall are present in the stomach and smallintestine. Coprecipitation, which was observed in the presence of cholic acid, ofcholesterol with deconjugated bile at acidic pH contributed to the reduction ofcholesterol in vitro. However, coprecipitation is not likely to take place in vivo sincethe pH in the small intestine is higher than neutral. Results from this study indicatethat the in vivo hypocholesteremic ability is likely due to the assimilation ofcholesterol by L. acidophilus cells or/and attachment of cholesterol to the surface of L.acidophilus cells.