There is a risk that patients can catch a range of infections during any stay in a hospital. A recent UK Office of Health Economics report highlighted that 10% of in-patients contract a hospital acquired infection from one source or another. There are many sources of infection but one specific route is via the surgical wound during an operation. Bacteria can be carried from the source to the wound site by currents of air causing post-operative infection at a later date. Even though clean air is delivered from the theatre ventilation system it is often contaminated with micro-organisms such as those originating from the skin of the operating staff and the patient themselves. At the start of the project, a physical model of a typical theatre with a laminar-flow air inlet in the ceiling was built and used to collect air velocity and temperature data. The experimental data was then compared to results simulated by a Computational Fluid Dynamics (CFD) model Once confidence had been gained in the simulation process, an actual theatre was computationally modelled. The aim of the research was to test various ventilation scenarios to observe how room parameters affect the air-flow paths in theatres. Once this had been completed, ways to re-direct contaminated air away from the operating table and other critical areas of the theatre to reduce post-operative infection rates were examined. The research showed that CFD is a suitable tool for visualising air-flow patterns in operating theatres and the results highlighted improvements that could be made to the design of new theatres and modifications which could be made to existing ones.