Purpose: We aimed to examine p16 protein expression in ovarian serous neoplasms along with normal ovarian tissues. Materials and Methods: p16 expression was immunhistochemically evaluated in 86 ovarian serous neoplasms (21 cystadenomas, 20 borderline tumors and 45 carcinomas) and 21 non-neoplastic ovarian tissue. The results were also compared with histopathological grade in serous adenocarcinomas. Results: p16 expression rates for benign, borderline ovarian tumors and ovarian cancer were 14.2%, 85% and 86.6%, respectively. It was significantly higher in carcinomas (p < 0.001) and borderline tumors (p < 0.001) compared to cystadenomas. No immunoreactivity was found in the non-neoplastic ovarian surface epithelial cells. The percentage of p16 expression did not change significantly with histological grade in carcinomas. Conclusion: p16 expression is strong and widespread involving most tumor cells in serous papillary ovarian carcinomas, and is probably an early event.