In most developed countries, ovarian carcinoma is the second most common malignancy of the female genital tract, following endometrial carcinoma. This chapter reviews the major morphological sub-types of ovarian carcinoma including their pathogenesis, and discusses problematic areas in typing. Most of the grading systems are universal in that they can be applied to all the major morphological sub-types of ovarian carcinoma. The major morphological sub-types of ovarian carcinoma are serous, endometrioid, clear cell and mucinous. Two relatively recent population-based studies that included central pathology review have provided updated information regarding the relative frequencies of the major sub-types. The perceived relationship between benign, borderline and malignant ovarian serous neoplasms was controversial. The morphological features of ovarian carcinomas treated by chemotherapy often differ markedly from native tumours. The chapter also summarizes the evidence that most high-grade pelvic serous carcinomas arise from the fimbria of the fallopian tube.