Expression of the c-myc gene was analyzed in 56 human primary ovarian cancer tissues, including 51 common epithelial and 5 non-epithelial tumours to determine molecular events in the carcinogenic process in ovaries. Over-expression of the c-myc gene was found in 37.3% of all ovarian tumour tissues, and in 63.5% of serous adenocarcinoma tissues. Significant over-expression of the c-myc gene at Stage III compared with other stages, and one remarkable case of over-expression in a serous tumour of low malignant potential suggest that c-myc expression is temporarily activated at some stage(s) during tumorigenesis of ovarian cancer, especially of serous tumours.