OBJECTIVES: To gain insight in the total Costs of 1st line treatment of NSCLC phase III/IV in the Dutch hospital setting To calculate the Budget Impact of adding Iressa (gefitinib), including EGFR mutation testing, to the treatment sequence. To identify costs of EGFR mutation testing. METHODS: A budget impact model was constructed by Medaxial and adapted by AstraZeneca the Netherlands to better reflect the Dutch situation. The model calculates the budget impact of EGFR testing and the resulting therapy change for NSCLC patients in Dutch hospitals.  The model covers the first line treatment of NSCLC fase IIIb/IV patients and calculates total costs in a hospital setting and budget impact, taken into account the following costs: - Medication - EGFR mutation testing - Administration and monitoring - Treating grade III/IV adverse events The model also calculates - Costs of delivery of oral therapies (outside hospital costs)  RESULTS: Before introduction of Iressa, total costs of 1st line NSCLC treatment in Dutch hospitals was €41,982.936. After introduction of Iressa, total costs in hospital setting slightly decreased to €41.939,604 (year 1). Cost of EGFR mutation testing is €198,432, but medication costs of the hospital will decrease with €248,193. CONCLUSIONS: Adding extra diagnosis will introduce new costs to the NSCLC treatment. However, for a individual hospital, the extra costs are limited. And the total costs of 1st line NSCLC treatment even decrease, since the reimbursement of Iressa is outside of the hospital budget. As a result, the hospital has less costs if patients are tested and the appropriate patients then treated with Iressa. At the moment, for some hospitals EGFR mutation testing is still seen as a hurdle. Apart from the ethical point of view (making sure patients will receive the medication they will benefit most from) also from costs perspective it is worth to test.