OBJECTIVE: To determine the feasibility,tolerability, and safety of the ultrasound assessment of tubal patency using foam as contrast. METHODS: This was a prospective multicenter study of 915 infertile nulliparous women scheduled for sonohysterosalpingography with foam instillation (HYFOSY) for tubal patency testing as a part of the fertility workup. Clinical and sonographic data were recorded into a web-shared database. Tubal patency, cervical catheterization, pain during the procedure and post-procedural complications were collected. Patients reported discomfort or pain experienced during the procedure with a visual analogue scale (VAS) score. RESULTS: Nine hundred fifteen women were included in the final analysis. Median age was 34 (range, 21-45) years and median body mass index was 23 (range, 16-41) kg/m2. Of 839 women, only 8(0.95 %) cases were abandoned due to impossibility of introducing the intracervical catheter. Most of the cervical os were easily cannulated with either paediatric nasogastric probes or special catheter for intrauterine insemination / sonohysterosalpingography 688/914(75.3 %). With a median instillation of 4 mL (range 1-16) of foam, both tubes were identified in 649/875 (70.9 %) patients, while unilateral patency was observed in 190/875 (20.8 %). Only 36/875 (3.9 %) of the women had bilateral tubal obstruction. The median VAS score for perception of pain during HyFoSy examination was 2 (range 0-10), and only 17 (1.9 %) of women reported severe pain (VAS ≥ 7). Pain was unrelated to tubal patency or tubal blockage. Unexpectedly, difficult cervical catheterizations that needed tenaculum, were more likely associated with mild pain during procedure [nasogastric probe group 176/289 (70.9 %) vs. insemination catheter group 166/399 (41.6 %) vs. tenaculum group 190/218(87.2 %) p < 0.001]. Finally, among 915 patients, we only noticed 3 (0.32 %) complications of the technique: two vasovagal episodes and a mild urinary infection. CONCLUSION: HYFOSY is a feasible, well-tolerated and safe technique for the evaluation of tubal patency in infertile women.