Purpose: To check the pathologic changes of focal adenomyosis after heat therapy using radiofrequency and to evaluate which approach – endometrial ablation or direct heat therapy – is better for adenomyosis. To evaluate whether the timing of the procedure and the menstrual cycle are related to pathologic outcomes after heat therapy. Methods: This study included nine women who underwent total hysterectomy for adenomyosis (diameter, ≥ 6 cm). Six fresh uteri were excised in the midline and subjected to radiofrequency heat therapy at the center of the adenomyomas (direct heat therapy) and three uteri were subjected to endometrial ablation. Thereafter, 1 cm3 myometrial tissue was obtained at 1 cm, 2 cm, and 3 cm away from the endometrium. Tissue sections were stained with hematoxylin and eosin. Immunohistochemical analysis using antibodies against cytokerain-19 (CK-19), actin, and estrogen receptor/progesterone receptor (ER/PR) was performed to evaluate CK-19 (endometrial epithelium marker), actin (myometrial marker) and ER/PR (checking the state of the menstrual cycle), respectively. Results: After endometrial ablation, cauterized tissues were not noted 2 cm away from the endometrium. All tissues between the endometruim and center of adenomyosis were cauterized after direct heat therapy. During the uterine proliferative phase, unlike the secretory phase, subendometrial layers were cauterized 10 min after direct cauterization. Conclusion: Direct heat therapy is more effective than endometrial ablation in adenomyosis, and heat is conducted effectively when the patients are in the proliferative phase.