Prison officers' knowledge and perceptions of hepatitis B, hepatitis C and HIV were explored by conducting a cross-sectional survey in four Dublin prisons with high rates of blood borne viral infections among the inmates. Most officers (87%) reported not knowing enough about these diseases to enable them to take the necessary precautions at work. Longer serving and senior officers were less fearful and less anxious about contracting the infections. Officers who had received hepatitis B vaccination were no less worried about hepatitis B than unvaccinated colleagues. Training on blood borne viruses had little effect on prison officers' knowledge or perception of blood borne viral infections.