Abstract: Mosquito-nets were sprayed with 9.6mg deltamethrin per square meter for control of malaria vectors in Yibin County, Sichuan Province in 1986- In the study area, the relative population indices of Anopheles anthrcpophagus and An sinensis in 35 mosquito-nets were 0.6 and 1.4 respectively; the man biting rates of these two vectors dropped by 97.8 and 90.8% respectively. The residual toxic effect of sprayed mosquito-nets, up to 104 days after spray, caused a mortality of 93.1-100% of An. anthropophagus and 87.1-100% of An. sinensis. The multiparous mosquito rate dropped by 48.4 and 51.3%. Indoor-intruding An. anthropophagus and An. sinensis were reduced by 76% and 78.3% respectively. The incidence of malaria decreased by 94.4%, the positive rate in school children declined by 77.5%. Both entomological and epidemilogical indices indicated that mosquito-nets sprayed with deltamethrin could effectively control the malaria prevalence. This measure is economical and practical for control of malaria.