ABSTRACT Phlebotomus papatasi is one of the common sand flies that found in Egypt. Three to five- days old 1080 non infected P. papatasi sandfly females were used in this study. They fed for 90-100 min. on blood of non immunized hamster for one time/week. Each hamster was re-exposed for an average of 18 exposures at one week interval after being immunized.  immunized. Sand flies were observed to determine their biting activity as Fed or Half-fed. Then sera of control and immunized hamster was analyzed by using spectrophotometer. Three replicates of sand flies groups (each with 360 insects) were used. The results indicated a remarkable change in biting activity of sand flies through the investigated period (18 weeks) where a powerful biting through the first seven weeks was observed, followed by a significant decrease in number of biting activity during the rest of weeks. This can be explained by acquiring hamster immunity due to formation of antibodies in his blood. Multiple exposures to sandfly saliva induce an immune response in hamster which can control leishmaniasis in this animal. This immune response was reflected in results of total protein estimation where the total protein increased after successive bits compared to control. Therefore, we could concluded that the antibodies which have been formed in hamster against saliva of female sandfly have a repellent effect as well as immunized effect. Knowledge to be gained from the present study will contribute to recent trends in the future development of novel strategies for preventing disease transmission in Egypt.