Aim: In 2007, the National Patient Safety Agency performed a study demonstrating that errors in prescribing led to nearly 12,000 adverse clinical incidents a year. The following year, they issued a rapid response report entitled 'Reducing Dosing Errors with Opioid Medicines' designed to be implemented by all NHS trusts. We performed a prevalence study to assess opioid prescribing errors in our large multi-speciality teaching hospital prior to implementation of these recommendations. Methodology: We conducted a 1 day snapshot of opioid prescriptions on inpatient drug charts. For every chart, all opioid information was entered into the study proforma. All data were reviewed by consensus group and errors categorised by quality and whether they were potentially lethal, serious, significant or minor. Results: A total of 330/722 (46%) charts were found to have opioid prescriptions. On the study day, there were 74 charts with errors and on expert review another 16 erroneous charts were found giving a total of 90/330 (27.2%). The largest quality statement error group was 'unclear prescription, missing information'. There were 4 potentially lethal, 26 serious, 38 significant and 22 minor errors. Discussion: Previous studies have reported opioid prescription error rates of 51.2-70%. Compared with the opioid literature, our trust fares well with an error rate of 27%- four of these errors being potentially lethal. This study has identified where there are weaknesses in our hospital opioid prescribing practice and has aided us in rewriting our acute and chronic pain guidelines with the explicit inclusion of the National Patient Safety Agency recommendations. We have also disseminated the study results at the Trust academic meeting and developed an opioid e-learning package which will be mandatory for all new staff.