Abstract: Phlebotomus chinensis were fed respectively on two groups of Cricetulus barabensis infect-ed with Leishmania donovani,of which one group had received deltamethrin bath and theother was not treated with insecticide bath.The results showed that all the sandflies in the former group died within 24 hours,whilethose in the latter group had a high survival rate. Among the 165 sandflies examined,114(69.1%)became infected.The promastigotes not only developed well in the midgut,but alsoinvaded esophagus,pharynx and proboscis.In the control group,the mortality of sandfliesin 24 hours was 5.1%(3/59).According to the data obtained in the present study,the authors consider that insecticidebath treatment of infected domestic dogs in endemic villages could be used for interruptingkala-azar transmission.