This prospective, multi-center, observational study will assess the progression-free survival and safety of patients with locally advanced or metastatic non-small cell lung cancer treated with Tarceva (erlotinib) and not disease progressing after at least 9 months. Data will be collected for 24 months.

Inclusion Criteria:

• Adult patients, >/=18 years of age
• Diagnosis of locally advanced or metastatic non-small cell lung cancer (NSCLC, stage III/IV)
• Treatment with Tarceva monotherapy and not progressing after at least 9 months at the date of study start

Exclusion Criteria:

• Not agreeing to be followed-up (for a maximum of 24 months)

Adult patients with non-small cell lung cancer