Rapid onsite evaluation is a technique that allows for real-time initial interpretation and appropriate triage of samples. Within pulmonary medicine, rapid onsite evaluation was initially utilized with conventional transbronchial needle aspiration to guide sampling location and ensure adequacy; however, it has become more popular with the expanded use of endobronchial ultrasound transbronchial needle aspiration. Although rapid onsite evaluation may not increase diagnostic yield during endobronchial ultrasound transbronchial needle aspiration, it has been associated with decreased need for additional biopsies, needle passes, and rates of complication. As lung cancer care has evolved over the last decade, the use of rapid onsite evaluation to help triage specimens and help procure appropriate specimen for ancillary testing has caused a renewed interest. Rapid onsite evaluation remains a labor-intensive endeavor, which requires experienced cytopathology team members to handle specimens, create slides, and provide real-time interpretation. This chapter reviews the current literature detailing the use of rapid onsite evaluation in interventional pulmonary procedures.