This study is designed to identify biomarkers which may predict improvement in progression free survival from treatment with Tarceva, in patients with advanced pancreatic cancer who failed one prior regimen of standard chemotherapy or who are deemed unsuitable for chemotherapy. It will also assess the efficacy and safety of Tarceva in this patient population. Patients will be randomized to receive either Tarceva 150mg/day po, or placebo po daily. Tumor tissue will be used for biomarker analysis. The anticipated time on study treatment is until disease progression, and the target sample size is 100-500 individuals.