OBJECTIVES: The extent to which individual lung cancer patients undergo guideline-recommended molecular testing in routine care prior to initiation of first-line erlotinib is not known. Prevalence and factors associated with testing and erlotinib therapy were determined in Stage IV non-small cell lung cancer (NSCLC). METHODS: We identified incident cases diagnosed between 2007-2009 using SEER-Medicare data. Multivariable models were used to identify factors independently associated with (1) molecular testing and (2) receipt of first-line erlotinib therapy. RESULTS: Only 6.5% (500/7,678) were treated with first-line erlotinib and of those, only 8.6% underwent a molecular test.  Testing and erlotinib therapy were independently associated with phenotypic enrichment using correlates of epidermal growth factor receptor (EGFR) mutations (female gender, Asian ethnicity, non-squamous-cell histology).  Older age, Medicaid enrollment, and admission to hospice decreased likelihood of testing but increased probability of erlotinib therapy.  CONCLUSIONS: Vast majority of NSCLC patients did not undergo molecular testing prior to treatment.  Clinical enrichment criteria were influential in patient selection for erlotinib therapy and testing, but these attributes do not adequately discriminate between EGFR mutation positive and wild type tumors. Provider education and payer mandates to submit test results before reimbursement for targeted therapies may encourage guideline-recommended implementation of these technologies.