7587 Background: Sentinel node (SN) can be detected in the drainage of many primary cancers and is considered a standard procedure in some tumors. For resectable lung cancer its study has began recently and its detection has not yet been standardized. Objective: To study the feasibility and safety of SN detection during surgery for lung cancer. Methods: Patients with non-small cell lung cancer, clinical stage I, amenable to surgery were eligible. Written informed consent was obtained in each patient before the procedure. Technique, as described by Liptay et al, consisted of four injections of albumin labelled with Technetium99, 0,25 mCi each peritumorally, and five minutes later, lobectomy and lymphadenectomy were associated with detection of SN (both in vivo and ex vivo). Results: From Jan 2006 to Nov 2008, the first 37 patients were included. In 35 patients one SN was detected, and in 2 there were two SN. SN was found in the lymphatic stations 10 or 11, except for tumors located in the left upper lobe, where two cases of a SN were found in station 5 and 6 each. In 23 cases of 37, both SN and lymphadenectomy were free of tumor. In seven of 37, SN was positive (in one, micrometastasis was detected with haematoxilin-eosin), and the rest of the nodes were free of tumor. In five of 37, SN and another node were positive. In two of 37, SN was falsely negative as one peribronchial node was positive but masked by radioactivity in the injected lung, one in right lower lobe and another in left lower lobe. Accuracy was 94,6%, sensibility 86%, specificity 100%, positive predictive value 100% and negative predictive value 92%. No relevant prolongation of surgery time was observed (5–15 minutes), and no morbidity or mortality related to this technique were seen. The cost of the materials used was 100 Euro per patient. Recruitment is ongoing. Conclusions: SN can be detected with a very high accuracy in lung cancer. This technique is feasible and safe, and does not add excessive cost or difficulty to the surgery of lung cancer. Modifications of the technique, using metabolic isotopes or new portatil 3D gamma detectors can be incorporated. Its final role in the staging and treatment of lung cancer is still unknown. Supported in part by a grant of the FIS (Fondo de Investigaciones Sanitarias), Spain. No significant financial relationships to disclose.