Background: Renal transplant patients of the Northern Territory (NT) of Australia, suffer poor transplant outcomes including graft rejection, infection and increased mortality, therefore requiring stringent immunosuppressive drug assay monitoring. Best practice dictates that drug assay results should be received within 24 hours and at the most no later than 48 hours post blood collection. Assays from the Royal Darwin Hospital (RDH) are processed at an interstate laboratory, therefore prolonging the time to dosage adjustment. Aims: To assess the time delay that exists between blood sample collection at the Royal Darwin Hospital (RDH) and the faxing of results from an interstate laboratory to RDH. Methods: We conducted a retrospective audit of immunosuppressive drug assay samples and results between the 4th of January 2013 and the 22nd April 2014. Time delay was divided into intervals: T1: Total time between collections to faxing of results back to RDH, T2: Time between blood collection, sending of samples and reporting at an interstate laboratory, T3: Time between results reporting and the faxing of results back to RDH. Results: A total of 389 drug assays from 49 renal transplant patients were analysed. Median times in hours (interquartile ranges) were T1=53.48 (31.68-78.55), T2=47.18 (28.80-76.18), T3=2.70 (1.87-3.90). 13.3 per cent of the results led to the requirement for dosage changes with the potential risk of under-dosing or overdosing. Conclusion: The long median time delay between sample collection and receiving of results illustrates the challenges of immunosuppression in this setting and the need for on-site immunosuppressive drug assaying.