Mutation of p53 gene is one of t.he commonest genetic changes in the development of human cancer including ovary. We intvestigated the diagnostic usefulness of the demonstration of p53 gene immunoreactivity in ovarian cancers, because immunochemical demonstration of p53 immunoreactivity is inexpensive, easily controlled and can be applied in routine pathology laboratories. p53 immunoreactivity was not identified in any patients in whom there was no morphological evidence of neoplasia. ln contrast, in contrast, in 46% of patients of ovarian cancer, p53 immunoreactivity was identified. Overexpression of gene correlated with advanced stage but did not corre1ate with grade, cell type and tumor size.