Since its approval in April 2018, osimertinib has been widely adopted as first-line therapy for patients with advanced -mutant non -small cell lung cancer (NSCLC). Understanding osimertinib resistance mechanisms and currently available treatment options are essential to selecting optimal second line therapy for patients whose disease progresses during front-line osimertinib. Using data compiled from 6 osimertinib-resistance series, we describe here the heterogeneous profile of EGFR-dependent and independent mechanisms of osimertinib treatment failure. We identified alterations (7%-24%), C797X (0%-29%), SCLC transformation (2%-15%), and oncogene fusions (1%-10%) as the most common mechanisms of resistance. This review provides an evidence-based, algorithmic approach to the evaluation and management of post-osimertinib progression as well as a compendium of active, enrolling clinical trials for this population.