The effects of infection following implantation of an orthopaedic prosthesis are devastating. The prevention of perioperative contamination is therfore of the utmost importance in arthroplasty. We undertook a prospective study to assess bacterial contamination in elective arthroplasty surgery. Splash bowls containing sterile saline are used to store and clean instruments used during the course of a procedure. The incidence of bacterial proliferation in splash bowls was examined as a marker of intra-operative contamination. A 100mL aliquot of fluid was removed from the splash basin at the end of the procedure and passed through a grid membrane using a vacuum pump. The membrane filter was then plated on chocolate agar and colony counts recorded at 24 and 48 hours. Organisms were identified by standard techniques. Demographic data, and perioperative data including the duration and type of procedure, the number of scrubbed and other personnel in theatre and the type of skin preparation and gowns used were also noted. A total of 43 cases were examined. 14 samples yielded positive cultures. Staphylcoccus was the most commonly cultured organism (9 cases). Four patients grew Pseudomonas species. Five patients grew other Gram-negative organisms including Neisseria and bacillus subspecies. Five patients grew multiple organisms. Mean duration of follow up was 8.4 months (range 6 – 18 months). None of the patients with contaminated samples developed any clinical signs of infection in the perioperative period; nor was there clinical or radiological evidence of infection or loosening on subsequent follow up. Despite the use of a laminar airflow system in all cases, in excess of 30% of cases were contaminated. This study underlines the importance of adhering to rigorous protocol in theatre including minimising theatre traffic and the use of antibiotic prophylaxis.