Summary: The recommendation to test every woman for gestational diabetes mellitus (GDM) has a defined cost. The management of women diagnosed with GDM will use additional health resources. This study examines the cost and resource utilization of a consecutive group of women diagnosed over a 1-year period. The cost of testing a woman for GDM is around $10.00 with slight variations depending on the testing procedure. The annual cost of testing in NSW would be less than 1 million dollars. Women diagnosed with GDM used the resources of a diabetes education centre for an average of 2.8 hours and attended for 3.4 (2.3) medical visits. Insulin was required by 18.7% of the women for 9.7 (4.7) weeks using 47.7 (21.2) units each day. Testing women for GDM is a low-cost item. Managing a woman diagnosed with GDM may cost several hundred dollars. Cost reductions could be made by reducing the amount of insulin used and by avoiding hospitalization.