The aim of this paper is to investigate the existence of moral hazard in the Brazilian health system. The dataset used is the 1998 PNAD (Pesquisa Nacional por Amostra Domiciliar), a Brazilian household sample survey. Brazilian health system is characterized as a mixed system: the public sector guarantees a full and free access for all individuals, whereas the private insurance is allowed to dispose supplemental health coverage. Nowadays, 25% of the whole population has private insurance. This analysis relies on a household heads sample, since they are responsible to the family decision to purchase supplemental plan. Two variables of healthcare utilization have been selected: medical visits and the number of inpatient days. These variables represent different types of healthcare and processes of making decisions. We estimate the over utilization in the private sector using a counter-factual analysis. The main findings suggest a moral hazard for both types of healthcare: for the visits model, we found that each individual in the private sector uses 32% more services than if they only have access to public services. For inpatient days, we found that each individual in the private sector uses 56% more services than if they only have access to public services.