The aim of this study was to investigate the effects of erythromycin on cows myometrium in vitro. After myometrial samples was contracted with oxytocin 0.6, 1.2, 1.8, and 2.4 mM erythromycin was applied and effects on peak amplitude and frequency of contractions were investigated by 10 minute intervals. The frequency of oxytocin-induced contractions was 10.88±3.25 whereas 14.0±2.70, 22.22± 3.40 (P<0.001), 17.55±2.29 (P<0.001) and 3.66± 1.8 (P<0.001) after application of 0.6 mM, 1.2, 1.8 and 2.4 mM erythromycin, respectively. The mean peak amplitude of oxytocin-induced contractions was 3.54±0.54, after application of 0.6 mM, 1.2, 1.8 and 2.4 mM erythromycin dose-dependently decreased the amplitude values to, 3.17±0.64 (P<0.001), 2.14±0.77 (P<0.001), 1.79±0.37 (P<0.001) and 0.7±0.41 (P<0.001), respectively. In conclusion, it was found that erythromycin in low doses inhibited amplitude of contractions but increase frequency, whereas high doses of erythromycin inhibited both amplitude and frequency of oxytocin-induced contractions of myometrium obtained from cows.