In scientific societies, as in other social fields, women's participation in decision making is lower than that of men. We describe the situation in SESPAS (Spanish Society of Public Health and Health Services Administration) where, despite representing a 40% of its members, very few women have been in positions in which decisions are taken or in those of professional recognition. The process of change implemented during recent years and some of the effects of the actions taken are presented. Making the existing inequalities known has generated debate and interest in the intervention. A gender and public health working group was set up. In the last two years more women have been promoted to more senior positions in SESPAS.