Deep endometriosis is associated with severe painful symptoms that sometimes impair the quality of life in women of reproductive age. Medical therapy does not provide for adequate pain relief, and an effective management option to reduce pelvic pain appears to be complete laparoscopic removal of as many endometriotic lesions as possible. In this study, we investigated the usefulness and risks of radical laparoscopic removal of deep endometriosis for patients diagnosed as stage III/IV endometriosis during laparoscopic surgery. Forty-seven consecutive patients undergoing conservative laparoscopic surgery alone (adhesiotomy and cystectomy of ovarian endometriosis but not removal of deep endometriotic lesion; non-DEL removal group) and 151 consecutive patients undergoing radical laparoscopic removal of deep endometriotic lesions combined with conservative surgery (DEL removal group) were compared. As a result, significant improvements in pain were obtained in both groups, however, the degree of improvement was significantly higher and the rate of recurrence was significantly lower in the DEL removal group. The addition of radical removal of deep endometriotic lesions to conservative laparoscopic surgery markedly reduces the severity of dysmenorrhea and the rate of recurrent pelvic pain. Although the surgical procedure is technically demanding, the levels of peri-operative complications and morbidity are acceptable.