The inheritance of the phenthoate-selected diamondback moth (DBM) was investigated, and the cross resistance was also examined against various insecticides. The phenthoate concentration-mortality relationship between $F_1$ progenies ( $S_{♀}$ ${ imes}$ $R_{♂}$, $S_{♂}$ ${ imes}$ $R_{♀}$) obtained from reciprocal crosses with the susceptible (S) and phenthoate-selected DBM strains (R) indicated the absence of sex-linked inheritance. The resistance ratios of $F_{1S}$ ( $S_{♀}$ ${ imes}$ $R_{♂}$), $F_{1R}$ ( $S_{♂}$ ${ imes}$ $R_{♀}$), and phenthoate-selected(R) strains were 23.8, 24.1, and 175.1, respectively. Degrees of dominance of the $F_{1S}$ and $F_{1R}$ progenies were 0.23 and 0.45. These results suggest that the inheritance of phenthoate resistance in DBM is controlled by one or more autosomal genes in a manner of incomplete dominance. This R strain exhibited a high level of cross resistance to parathion, pyrachlofos, and phosmet with resistance ratios of 51.1, 59.9 and 72.5, respectively, and also showed medium level of cross resistance to most organophosphorus insecticides with the range of resistance ratios among 5.0∼50.0, except for acephate, demeton-S-methyl, profenofos, and pyridaphenthion showing low level of cross resistance with resistance ratios among 1.5-4.0. However, this R strain exhibited low level of cross resistance to most carbamate insecticides except BPMC showing resistance ratio of 5.3. Similar low level of cross resistance was observed from the pyrethroid and neonicotinoid insecticides with the resistance ratios among 1.2∼4.6.1.2∼4.6.