In a prospective clinical study (March 89-June 91), we examined 114 infertile women to evaluate the diagnostic value of trans-uterine tubal cannulation with the injection of sterile fluid and consecutive sonographical control in the assessment of tubal patency. The results of this technique were compared with the findings of laparoscopy and/or hysterosalpingography. With the Jansen-Anderson Catheter (J-A-C) it was possible to reach the isthmic part of the tube without any analgesia or anaesthesia. 10 to 15 ml of sterile culture medium were injected. In case of tubal patency the fluid was detectable in the pouch of Douglas by transvaginal ultrasound. In 108 out of 114 women (94.7%), the cannulation of at least one tube was possible. All 97 patients with patent tubes (laparoscopy) were diagnosed correctly via the J-A-C. The three cases of proximal tubal occlusion were also diagnosed correctly, 8 patients with one or two-sided hydrosalpinx were also recognized. All five patients with bilateral hydrosalpinx were detected. Three women showed a unilateral hydrosalpinx in the laparoscopy. In these cases the diagnosis obtained by the J-A-C was once bilaterally patent and twice bilaterally distally occluded. Trans-uterine cannulation of the tubes with injection of sterile fluid and consecutive transvaginal sonography is an easy and safe method to evaluate the tubal status. It becomes possible thereby to prove tubal patency in a very early stage of diagnostics. Loss of time and futile treatment cycles (stimulations or inseminations in cases of tubal occlusion) can thus be avoided.