The areas of study were two districts of Mamasani County, an agricultural area, located 200 km north of the Persian Gulf. The build-up of An. stephensi populations is incredibly rapid in July-August and decreases in November. The peaks of the populations are in July, August and early September. Catches on human and animal bait were carried out from 18.00-05.00 hr outdoors. On the basis of the data collected, it was found that biting was maximal from 20.00-24.00 hr. The average catch per bait/hr on man was lower than on cattle outdoors.