Pedro Pita Barros and Joana Gonçalves de Sá are part of the working group of the Roadmap for Serological Testing in Portugal, promoted by the Gulbenkian Institute of Science. Serological testing is a powerful tool for determining the spread and intensity of transmission that the virus reached during the first wave of the COVID 19. It is essential to know the real dimension of the epidemic in the country in order to better inform the decision-making process. This roadmap proposes primarily a national study with a sentinel population tested over time. This will allow to obtain reliable information on the epidemiological dynamics of COVID19 that will evolve in our populations for an indefinite period. This study will be decisive for Portugal to be seen as an example of rigor in the adoption of epidemiological surveillance measures focused on protecting our population.