The aim of this study was to investigated the effects of gentamicin on cat myometrium in vitro. After myometrial samples was contracted with 0.062, 0.125 and 0.250 mg/ml gentamicin was applied and effects on peak amplitude and frequency of contractions were investigated by 10 minute intervals. The frequency of oxytocin-induced contractions was 9.37±1.1 and peak amplitude was founded 3.41±0.45. Gentamicin dose dependently inhibits both amplitude and frequency of oxytocin-induced contractions of myometrium. Gentamicin dose-dependently decreased the the frequency values to 6.4±1.0(P<0.001), 4.0±0.66(P<0.001) and 0.18±0.4 (P<0.001). The mean peak amplitude of gentamicin dose-dependently decreased the peak amplitude values to 3.27±0.45(P<0.001), 2.90±0.37(P<0.001) and 0.18±0.4(P<0.001) respectively. In conclusion, it was found that gentamicin inhibits both amplitude and frequency of oxytocin-induced contractions of myometrium obtained from cat.