Background Independent prescribing of medicines by nurses is widely considered to be part of advanced nursing practice, and occurs within an episode of patient care that can be completed independently by a nurse. Nurse prescribers therefore require the competencies necessary to manage a consultation--such as history taking and diagnostic skills--and subsequently need to decide on any appropriate medicine to be prescribed. Safe prescribing should also involve an accurate, legible and comprehensive written prescription and documentation of the consultation in the patient's records. However, the extent to which nurse independent prescribers use prescribing competencies and standards in practice had not been researched prior to this study. Aim To describe the frequency with which nurses use a range of prescribing competencies in their prescribing consultations, in order to provide a measure of the quality and safety of nurses' independent prescribing practices. Design and methods Across 10 case study sites, 118 nurse independent prescribers' prescribing consultations were analysed using non-participant observation and a structured checklist of prescribing competencies. Documentary analysis was also undertaken of a) prescriptions written (n =132) by nurses and b) the record of the prescribing episode in patient records (n =118). Sample and setting 118 prescribing consultations of 14 purposively selected nurse independent prescribers working in primary and secondary care trust case study sites in England. Findings Nurse independent prescribers were issuing a prescription every 2.82 consultations; nurses used a range of assessment and diagnosis competencies in prescribing consultations, but some were employed more consistently than others; nurses almost universally wrote full and accurate prescription scripts for their patients; nurses recorded each of their prescribing consultations, but some details of the consultation and the prescription issued were not always consistently recorded in the patient records. Conclusion The findings from this observation study provide evidence about the quality and safety of nurses' prescribing consultations in England.