To determine the prevalence of p53 abnormal protein expression in transitional cell carcinoma of the ovary in Peking Union Medical College hospital, and to analyse the correlation between the overexpression of p53 protein and prognostic parameters of transitional cell carcinoma of the ovary, thirty-two transitional cell carcinoma of the ovary and 20 normal ovaries were analysed. Detection of overexpression of p53 protein was carried out by immunohistochemical staining (IHS) using the monoclonal antibody DO-1 on paraffin sections. 41% of 32 samples of transitional cell carcinoma of the ovary showed positive IHS with DO-1, whereas only 5% of 20 normal ovaries showed weakly positive cytoplasmic staining (P < 0.01). p53 overexpression did not correlate with age, CA125 levels, histological grade and lymph node metastasis, but patients with overexpression of p53 had a poor prognosis. Overexpression of p53 is a more common event in transitional cell carcinoma of the ovary. Further studies are warranted to clarify the role of p53 in transitional cell carcinoma of the ovary.