Our scanty knowledge of the pathology of early malignant change in the ovary is reviewed. The concept of ovarian intraepithelial neoplasia is discussed, and the malignant potential of ovarian cystadenomas is considered. The question of overt malignant change in tumors of borderline malignancy is reviewed. It is concluded that any advance in our understanding and our knowledge of the early stages of malignant change in the ovary will only come from the use of newer techniques that allow a more sophisticated approach than that allowed by purely morphological methods.