The 5-year survival rate for patients with stage III non-small cell lung cancer (NSCLC) is 10%. A number of genetic alterations are associated with this disease including mutations and amplifications of EGFR (70%) and Ras (20-30%), both of which are upstream of PI3K. Our previous data show that these regulate tumor radiation sensitivity. Here we ask whether the activation of this pathway has prognostic relevance in NSCLC. Two series of patients were retrospectively analyzed. The first series consisted of 23 Stage III NSCLC patients treated preoperatively with a chemo/radiation protocol. The second consisted of 12 Stage III NSCLC patients treated with chemo/ radiation without surgery who had survived more than 2 years. Expression levels of EGFR and Her-2 were assessed by immunohistochemical staining. PI3K signaling was evaluated by staining for phosphorylated Akt (P-Akt), a downstream target of PI3K. The staining for EGFR, Her-2, and P-Akt were related to outcome in the two groups. Additionally, the importance of PI3K signaling was evaluated in 3 NSCLC cell lines using a pharmacological blockade of PI3K by LY294002. In the first series of patients, 43% were positive for EGFR, 5% for Her-2, and 82.6% for P-Akt. Of the survivors, 25% were positive for EGFR, 0% for Her-2, and 42% for P-Akt. For P-Akt, this difference had a probability calculation of 0.003. The three NSCLC cell lines that we tested were found to have high levels of P-Akt. Pharmacologically inhibiting PI3K led to decreased Akt phosphorylation and radio sensitization of all three cell lines. The finding that NSCLC survivors treated by radiation have lower levels of PI3K and Akt signaling is consistent with the idea that inhibition of Akt leads to radio sensitization. This further suggests that Akt might be a useful target for sensitization of NSCLC to radiation.