The RTFNB (Reunião de Trabalho sobre Física Nuclear no Brasil) is a traditional nuclear physics annual meeting organized by the Brazilian Physical Society (SBF) since 1978. The XXXI-RTFNB was held at the city of São Sebastião, at the northern shore of the state of São Paulo, from 8 to 12 of September, 2008. The meeting took place at the Maresias Beach Hotel, which is located very close to the beach. The hotel provided a wonderful view to the sea and a nice environment where the participants could share their ideas, experiences and explore possibilities for collaborations in a relaxing atmosphere. We have received many positive remarks from the participants both during and after the conference, and we believe that the event has proved to be a fulfilling experience for all those who took part in it. Nearly 130 participants attended the meeting, being 14 from foreign institutions (11 invited speakers), 75 PhD researchers from national institutions, and 38 graduate students. The event program covered topics of great interest from many areas of nuclear physics. The contributions to the conference could be divided into the following sub-areas: Applied physics: 10 oral communications and 29 posters.Low energy nuclear physics: 11 oral communications and 26 postersHigh energy nuclear physics: 8 oral communications and 5 posters.