This study examined the practice of preoperative fluid restrictions and the influence of the hospital ‘nil by mouth’ policy on clinical practice. Structured interviews were used to assess the knowledge of nurses and anaesthetists relating to current hospital policy, their attitudes to fluid fasting and the constituents of clear fluids. The interval between the last intake of fluid and the induction of anaesthesia was measured in 90 adult patients to determine actual periods of fasting. It was found that most patients on the same operating list commenced fasting simultaneously with little or no attempt made to individualize the timing which contributed to prolonged periods without fluids, ranging from 3 hours 30 minutes to 17 hours and 45 minutes. Only 30% of nurses were aware of the hospital policy compared with 75% of anaesthetists. The evidence from this study demonstrated that the hospital policy was not reflected in clinical practice which continued to be based on tradition.