Ovarian tumors of low malignant potential (LMP) are intermediate between benign adenoma and frank ovarian carcinoma, and are characterized by the absence of destructive stromal invasion, or microinvasion. If LMP did not develop into invasive carcinoma, then a minimally invasive simple treatment could be chosen. However, histological diagnosis cannot completely predict the prognosis of patients with ovarian tumors. It was found that mucinous LMP is most frequent in Japan, whereas serous LMP is the most common in Western countries. Mucinous LMP with loss of heterozygosity (LOH) at chromosomes 5q14-21 and 17q11.2, and serous LMP were suggested to be precursor lesions of ovarian carcinomas. Follow-up study revealed that patients with mucinous LMP who had LOH at 19q12 and/or Xq11-12 were at the greatest risk of progression. It is concluded that molecular genetic analysis such as LOH study could predict prognosis and aid in treatment decision-making. The present review describes molecular genetic changes of LMP and presents problems on LMP that remain to be elucidated.