Uterine contractility was evaluated in 30 women, 16 with endometriosis and 14 controls. Two catheters were introduced into the uterine cavity, one next to the fundus and the other in proximity of internal os. They were connected to a pressure transducer that transforms mechanical events into an electrical signal, and analyzed by a system dedicated to this purpose. Data were analyzed by unpaired Student's t and McNemar tests. Frequency and amplitude of oscillations and mean pressure uterine tone were evaluated. Frequency of oscillations in the fundus (mean &plusmn; SD) were significantly higher in women with endometriosis than in controls: 21.86 &plusmn; 9.75% at 10 minutes versus 10.20 &plusmn; 5.26%, respectively (p <0.04). The mean basal pressure tone was also higher than in controls: 55.54 &plusmn; 21.04 mm Hg and 25.28 &plusmn; 19.94 mm Hg, respectively (p <0.04). Abnormal uterine contractility in women with endometriosis may be associated with a possible tubal efflux of endometrial tissue and its ectopic implants.