Technical Abstract: Cross-resistance to two fipronil analogs, butene-fipronil and ethiprole were detected in fipronil-resistant field populations and a resistant laboratorial strain of the brown planthopper, Nilaparvata lugens, although the two analogs have not been used widely in rice-growing areas in China. The results showed that six field populations with 24.7~44.9-fold resistance to fipronil had reached a higher level of cross-resistance to ethiprole (RR=45.1~96.6-fold) and had a minor level cross-resistance (RR=3.4~8.3-fold) to butene-fipronil. After 10 generation selections, resistance ratio to fipronil increased from 7.3-fold to 41.3-fold. At the same time, the insect increased cross-resistance ratio to ethiprole from 16.3-fold to 65.6-fold, while it had only minor increase in cross-resistance to butene-fipronil from 2.8-fold to 4.0-fold. These results confirmed that fipronil-resistant N. lugens could develop a higher level of cross-resistance to ethiprole, while it still maintained a lower level cross-resistance to butene-fipronil. Our data suggest that ethiprole is not a suitable alternative for controlling N. lugens, once the insect has developed a high level resistance to fipronil. Further investigation is necessary to understand the cross-resistance mechanisms in N. lugens.