In March 1992, the Royal College of Surgeons issued Guidelines for Day Case Surgery. Patients with a body mass index (BMI) > 30 were deemed unsuitable for operations to be performed as a day case. Since these guidelines were issued, many changes have occurred. Two years ago we successfully increased the BMI limit for patients undergoing general anaesthesia in our day surgery unit from 30 to 34. The success of this led us to question the current validity of the Royal College of Surgeons guidelines. A postal questionnaire was conducted surveying current practice in day surgical units within the UK. We achieved a 96% response rate. The results demonstrated a range of acceptable BMI values, with 85% of units anaesthetising patients with a BMI > 30. We conclude that many day case units routinely anaesthetise patients with BMI values > 30. Therefore, the current guidelines, which were issued 9 years ago, are no longer being adhered to nationally.