OBJECTIVES: Both insulin detemir and insulin glargine have been approved for reimbursement on the Australian Pharmaceutical Benefits Scheme (PBS).  Prior to their listing, intermediate acting insulin isophane (NPH) was the only PBS listed basal insulin.  Determination of the dose relativity from the randomised clinical trials was confounded due to strict titration algorithms and protocol requirements.  Therefore to ascertain the dose relativity in clinical practice, a chart audit was conducted. METHODS: The audit was carried out in six practices; five specialist and one primary care.  The inclusion criteria were: diagnosis of type 1 diabetes, switched to detemir or glargine between 01 October 2006 and 31 May 2007 and at least 6 months of follow-up. To ensure that there was no systematic bias, the investigator was instructed to select every nth file with n being a function of the number of patients who were eligible for participation. RESULTS: Records were obtained on 87 patients who switched to detemir and 77 patients who switched to glargine.  The baseline characteristics of patients were similar for both groups with the exception that 30% (26/87) of patients switched to detemir and 48% (37/77) of patients switched to glargine were having once daily injections of NPH.  Despite a regulatory label for only once daily dosing for glargine, the audit established that 25% of glargine use was twice daily. There was no statistically significant difference in baseline pre-switch NPH doses to either detemir (0.44 to 0.45 U/kg/day) or glargine (0.45 to 0.43 U/kg/day). The dose relativity between detemir and glargine final doses was one to one. The audit also demonstrated no statistically significant difference in HbA1c between detemir and glargine (8.0% & 7.8%, respectively).  CONCLUSIONS: The chart audit provided evidence that in the clinical practice setting, detemir and glargine are equipotent and deliver similar outcomes.