This paper studies the distributive aspects of the Brazilian social security system. Contributions made and received benefits for each individual were considered, in the period 1976-1999. The expected contributions and benefits flows of representative groups of individuals were then estimated. For each group, the internal rates of return inherent to the social security system were assessed. Groups with lower education levels achieve the highest rates of return. The rates are also different according to the country's regions. The rates of return have grown over the years. These results evidence the existence of distributive characteristics in the Brazilian social security system.