Viral hepatitis is one of the leading causes of disease around the world. In Latin America is a severe public health problem. We conducted a case-control study in the Cayetano Heredia Hospital, Lima, Perú, seeking for risk factors for hepatitis B infection. We found 0.41% of frequency of HBsAg and 8.13% of anti-HBs in the 492 persons screened. Contact with blood was confirmed as a risk factor for hepatitis B infection; disposable needle-wash was also identified as a major risk factor. The personnel of the Sterilization Room is also in high risk for the infection. The nurse-aid personnel was also identified as a high-risk group. We suggest that the needle wash is a risk factor very easy to remove, and also stopping the rotation of the auxiliary personnel could reduce the incidence of the infection in the personnel at risk.