Uterine smooth-muscle tumors of uncertain malignant potential(STUMP) cannot be categorized as benign or malignant. In this paper, the authors describe several cases presenting with STUMP. The authors reported five cases of STUMP treated in Soonchunhyang University Bucheon Hospital from 2013 to 2016. Four patients remain recurrence free (26-60 months) and one patient was lost to follow-up one month after STUMP diagnosis, revisited three years later, and was diagnosed with high-grade (Stage IIa) ovarian serous carcinoma after a staging operation. The authors suggested that regular follow-up after surgery was important in STUMP, and more aggressive surgical management, including salpingo-oophorectomy, should be considered.