In the UK, surveillance for surgical site infection is mandatory for orthopaedic surgery. NHS trusts must participate for at least one surveillance period (3 months) every year in at least one of four categories:- hip replacement, knee replacement, hip hemiarthroplasty or open reduction of long bone fractures. Surgical site infections (SSIs) are defined as infections related to a surgical procedure that affects the surgical wound or deeper tissues handled during the procedure. Since mandatory surveillance began in 2004, rates of SSIs have markedly decreased. This is postulated to be secondary to increased early detection. Shorter postoperative stays and underestimation are also likely to be influential factors. We reviewed 150 consecutive lower limb arthroplasties performed at a district general hospital from July to September 2007. All inpatient data were collected as part of the Health Protection Agencies mandatory surveillance. We reviewed this data and notes for recorded evidence of infections or complications for minimum of one year after surgery. We reviewed computer records for recorded microbiological evidence of infection preoperatively and postoperatively. The operations performed during the surveillance period were:- 60 primary total knee replacements (TKRs), 37 primary hip replacements (THRs), 25 hip resurfacings, 15 unicondylar knee replacements, 3 patello-femoral joint replacements, 6 revision TKRs and 4 revision THRs. No SSI’s were detected during the mandatory surveillance period (i.e the inpatient stay, mean 5.61 days, Range 2–44 days). Two SSI’s (1.33%) were detected in our follow up period. Both were superficial wound infections. The first, a 53 year old hip resurfacing patient who was discharged 3 days postoperatively and developed Staphyloccocal infection 5 days later. The other was a 76 year old who underwent THR surgery, was discharged at day 6 and presented on day 12 with Pseudomonas wound infection. Both cases were initially diagnosed and treated successfully with oral antibiotic by GPs. One 61 year old patient who underwent hip resurfacing presented at day 62 with pain. X-rays showed loosening. Deep infection was suspected but hip aspirate, and inflammatory markers were negative. He is being monitored in the outpatient department. Our analysis also revealed that 3 patients had urinary tract infections (Coliforms on MSU) on the day of surgery and none have had postoperative complications. Intraoperative soft tissue samples for one patient who underwent one stage revision TKR grew Haemolytic Streptoccocus but there has been no evidence of postoperative complications. Other complications seen were THR dislocations (n=3) for reasons other than infection, 2 were revised. Persistent pain (n=2), common peroneal nerve palsy (n=1). We conclude that detection of SSI during inpatient stay is almost impossible. Mandatory surveillance seems excessive and a waste of resources