Öz In this study, multiple resistance, inheritance and cytochrome P450 enzyme activity were determined in Tetranychus urticae Koch (SAK) population after 20 selections for bifenthrin resistance. Selection study and LC50, 60 levels of SAK population of T. urticae were determined by dry film method. LC50 level of the SAK population selected twenty times with bifenthrin was increased from 984.49 to 11914.40 µl l-1 distiled water. Selected population showing 21.84 fold resistances was named as BIF 20 population. Bifenthrin resistant BIF 20 population showed low resistances against abamectin (4.73 fold), chlorpyrifos (4.72 fold), clofentezine (2.68 fold), propargite (2.04 fold) and fenpyroximate (1.72 fold). The inheritance of bifenthrin resistance with F1 females produced after reciprocal crosses between resistant and susceptible populations was found to be incompletely dominate and not sex-linked GSS, SAK and BIF 20 populations were investigated in terms of the enzyme activity of cytochrome P450. The cytochrome P450 activity increased from 0.00231 mOD/min/mg protein to 0.00310 mOD/min/mg protein in BIF 20 population which was resistant against bifenthrin.