Abstract: House flies, Musca domestica L. is a major and the most common urban insect pest in Indonesia and is known to have the ability to develop resistance to insecticides. In order to determine the resistance status of this pest to permethrin and imidacloprid, the most commonly used insecticides to control this pest, 32 strains of house flies collected in 2013 and 2014 from 26 capital of provinces in Indonesia were tested. House flies were tested by topical application and feeding bioassay for resistance to permethrin and imidacloprid, respectively. To examine the resistance mechanism to permethrin, the synergist piperonyl butoxide was used. Majority of all strains, 26 of 32 field-collected strains showed very high levels of resistance to permethrin, the range of resistance ratios was 190-25190 fold for permethrin when compared with a susceptible strain. However, a few strains showed no to high levels of resistance to permethrin, with the range ratio was 0.3-143 fold. Meanwhile, for imidacloprid, all strains showed no to very low resistance (resistance ratios of 0.4-6.1 fold). Assay using permethrin in the presence of PBO in 12 of 14 selected strains were found to decrease the LD values, which suggests that the detoxifying enzyme Mixed Function Oxidase (MFO) might have a role in the development of resistance to permethrin. Our study is the first report of house flies resistance throughout much of Indonesia, although all strains were still susceptible to imidacloprid. The findings, together with house flies integrated management, can be used to prevent resistance development in other insecticides.