The microplate method of an ELISA was modified for identification of human blood meals from 5,325 engorged mosquitoes belonging to 12 species of Anopheles captured in 19 provinces of Iran. Four hundred and four (7.5%) specimens reacted with the ELISA anti-human alkaline phosphatase conjugate. The human blood index in nine species of Anopheles varied from 3.6 to 23.7%. The results of this field application of the ELISA indicated that the technique is practical, reproducible and generally a suitable serological test for determination of human blood index of the anopheline mosquitoes.