The effect of n~ural falling and dipping of house flies on the degree of contamination of sterile water and milk was investigated. The study was made on sterile tap water and also on sterile water at pH 4, which represents the reaction of stOOlachfl uids. It was found that the total microbial flora showed progressing drop in their counts after 60 minutes incubation. Dipping treatments of house flies gave lower microbial contamination of water at pH 4 than at neutral pH. This trend was also observed for non-haemolytic and haemolytic microflora determined on blood agar medium. Dipping the house flies three times generally resulted in lower microbial count than natural falling and dipping once treatments. It was also found that complete dipping of fly in milk reduced the initial microbial contamination and retarded their growth. This paradoxial result is quite interesting since the logical condition, if the microbial load is only a matter of contamination without the influence of any other factor. is that dipping treatment would give higher figures than natural falling. All these observations