OBJECTIVES: We aimed to ascertain the efficacy of an intervention in which laboratory test costs were provided to clinicians as a pocketsized brochure, in reducing laboratory test costs over a 4-month period. METHODS: This was a non-randomised intervention study in the Internal Medicine wards at Steve Biko Academic Hospital, Pretoria, in which the intervention was laboratory test costs provided to clinicians as a pocket-sized brochure. The intervention period was the winter months of May - August 2008 and the pre-intervention period was the same months of the preceding year. In the two 4-month periods (2007 and 2008), the number of days in hospital and the laboratory tests ordered were computed for each patient admitted. For the intervention and control groups, pre- and postintervention cost and days in hospital were estimated. RESULTS: The mean cost per patient admitted in the intervention group decreased from R2 864.09 to R2 097.47 – a 27% reduction. The mean cost per day in the intervention group as a whole also decreased, from R442.90 to R284.14 – a 36% reduction. CONCLUSION: Displaying the charges for diagnostic tests on the laboratory request form may significantly reduce both the number and cost of tests ordered, and by doing so bring about considerable in-hospital cost savings.